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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
[5] Consideration of Pile Group Action
(1)Whenpilesareusedasapilegroup,theeffectofpilegroupactiononthebehaviorofindividualpilesisnecessarytobeconsidered.
(2)WhenthecenterintervalofdrivenpilesexceedsthevaluesinTable 2.4.10,theactionofthepilegrouponlateralresistancemaybeignored.
Table 2.4.10 Center Intervals of Piles
SandysoilTransverse Pilediameterx1.5Longitudinal Pilediameterx2.5
CohesivesoilTransverse Pilediameterx3.0Longitudinal Pilediameterx4.0
[6] Lateral Bearing Capacity of Coupled Piles
(1)Thelateralbearingcapacityofafoundationofthestructurewithcoupledpilesisnecessarytobedeterminedasappropriateinviewofstructuralcharacteristicsofthefoundation.
(2)DistributionofHorizontalForceinFoundationwithaCombinationofVerticalandCoupledPilesWhenahorizontalforceactsonafoundationwithacombinationofverticalandcoupledpiles,theforcebornebyverticalpilesisfarsmallerthanthatbornebycoupledpilesundertheconditionofequalhorizontaldisplacement.Itmaygenerallybeassumedthatallofthehorizontalforceisbornebythecoupledpiles.
(3)LateralBearingCapacityofCoupledPilesThere are two calculationmethods for the lateral bearing capacity of coupled piles. The first method onlytakes account of the resistanceof the axial bearing capacity of eachpile. The secondmethod takes accountoftheresistanceoftheaxialbearingcapacityofeachpileaswellasthelateralbearingcapacityofeachpileinconsiderationofthebendingresistanceofpiles.
(4)CasewhenOnlyAxialResistanceofIndividualPilesisConsideredasResistingHorizontalForce
Whenonlytheaxialresistanceisconsideredasresistance,asshowninFig. 2.4.19,theverticalandhorizontalactionsactingontheheadofapairofcoupledpilesshallbedividedintotheaxialforceofeachpile.Thecoupledpilesshallbedesignedinawaythattheaxialforceoneachpileislessthanthedesignvaluesoftheaxialresistanceordesignvaluesoftheaxialpullingresistanceoftherespectivepiles.Theaxialforcecanbecalculatedusingequation(2.4.46)oragraphicsolution(seeFig. 2.4.19)
(2.4.46)
where P1,P2:pushingforceactingoneachpileorpullingforcewhenthevalueisnegative(kN)θ1,θ2 :inclinationangleofeachpile(º) Vi :verticalforceactingoncoupledpiles(kN) Hi :horizontalforceactingoncoupledpiles(kN)
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Hi
Hi
Vi
P1
P1
P2
P2
Vi
θ1 θ2
Fig. 2.4.19 Axial Forces of Coupled Piles
(5)Method of Calculating Horizontal Resistance of Coupled Piles Considering Lateral Resistance of individualPilesVariousmethodsofcalculatingthehorizontalresistanceofcoupledpilesbyconsideringthelateralresistanceofindividualpilesareavailable.Forexample;
①Method of solution based on a conditionwhereby the displacement of each pile is always the same at theintersectionofthecoupledpiles,ontheassumptionthatthespringcharacteristicsofthepileheadintheaxialandlateraldirectionsareelastic.
②Methodofobtainingtheultimateresistanceofthecoupledpilesontheassumptionthattheaxialandlateralresistancesofthepilesshowelasto-plasticproperties.
③Methodofcalculatingtheloadanddisplacementatthepileheads,orthesettlementandtheupwarddisplacementofpilesbypullinginthecaseof(b)onthebasisofempiricalequations.110)
④Methodofusingtheresultsofloadingtestsonsinglepiles.111)
⑤Methodofsolutionassumingthattheyieldstateofeachpilewilloccursuccessivelyandtheresistanceofeachmembertogreaterforceswillbeconstantuntiltheresistanceofthecoupledpilesreachestheultimatebearingcapacity.Thefollowingpresentsanoutlineofmethod①.
Themethod①aboveistocalculatethedistributionofhorizontalforcetoeachpileontheassumptionthattheaxialandlateralresistancesofapilehaveelasticproperties112) InthecoupledpilesshowninFig.2.4.20,thesettlementofeachpileatthepileheadisproportionaltotheaxialforceactingonthatpileandalsothelateraldisplacementisproportionaltothelateralforceactingonthatpile.Onthisassumption,theaxialandlateralforcesactingoneachpileofthecoupledpilescanbecalculatedusingequation(2.4.47),derivedfromtheconditionsofforceequilibriumandcompatibilityofdisplacements.
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
(2.4.47)
Verticalandhorizontaldisplacementsofthepileheadcanbecalculatedbyequation(2.4.48)
(2.4.48)
where
N1,N2 :axialforceactingoneachpile,compressiveforceisindicatedbypositivevalue(kN) H1,H2 :lateralforceactingoneachpile(kN) V :verticalloadperpairofcoupledpiles(kN) H :horizontalloadperapairofcoupledpiles(kN) θ1,θ2 :inclinationangletoverticallineofeachpile(°) ω1,ω2 :axialspringconstantofeachpilehead(kN/m) µ1,µ2 :lateralspringconstantofeachpilehead(kN/m) δ'1,δ'2 :verticaldisplacementofeachpilehead(m) η'1,η'2 :horizontaldisplacementofeachpilehead(m)
Thesubscriptnumbersattachedtothesymbols,asshowninFig. 2.4.20,are“1”forthepushedpileand“2”forthepulledpileifonlyahorizontalloadacts. ThevalueslistedinTable 2.4.11 maybeusedforthespringconstantsofpilehead.ThesymbolsusedinTable 2.4.11aredefinedbelow
(2.4.49)
where :penetrationlengthofpiles(m) λ :exposedlengthofpiles(m) E :Young’smodulusofpilematerial(kN/m2) A :pilesectionarea(m2) I :momentofinertiaofpile(m4) Es :elasticmodulusofsubsoil(kN/m2)Es=kCH B B :pilewidth(m) κCH :coefficientoflateralsubgradereaction(kN/m3)
ThecoefficientoflateralsubgradereactionkCH maybecalculatedbymultiplyingthevalueofkCH obtained
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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in[4] Estimation of Pile Behavior using Analytical Methods, (5) ② Chang’s Method bythefactorobtainedfromFig. 2.4.17,inaccordancewiththeinclinationofpiles.
V
HN1 N2
H1
H2
(Out-batter pile) (In-batter pile)
l1 l2
λ1 λ2
δ1
δ2
δ'1δ'2
η1 η2
η'1 η'2θ1 θ2
Fig. 2.4.20 Coupled Piles Considering Pile Bending and Soil Resistance due to Deflection
Table 2.4.11 Spring Constants of Pile Head
Axialspringconstantofpilehead(ω)
EndBearingpiles
Frictionpiles
Cohesivesoil
Sandysoil
Lateralaxialspringconstantofpilehead(µ)
Pileheadhinged
Withoutexposedsection(λ=0)
Withexposedsection(λ≠0)
Pileheadfixed
Withoutexposedsection(λ=0)
Withexposedsection(λ≠0)
2.4.6 General Considerations of Performance Verification of Pile Foundations
Performanceverificationofpilefoundationscanbeconductedasfollows.
[1] Load Sharing
(1)Verticalloadsareconsideredtobesupportedbypilesalone.Ingeneral,nobearingcapacityshallbeexpectedfor thegroundincontactwith thebottomof thesuperstructure. Evenif thegroundunder thebottomslabofthesuperstructurewhichissupportedbythepilesisincontactwiththebottomoftheslabwhenconstructioniscompleted,voidsundertheslabwillappearovertime;therefore,fromtheviewpointofsafety,itispreferabletoignorethebearingcapacityofthegroundundertheslab.
(2)Horizontalactionsaregenerallysupportedbypilesalone.However,ifpassiveearthpressureresistanceatthefrontoftheembeddedpartofthesuperstructurecanbeexpected,thisresistancemayalsobeincluded.However,itisgenerallydifficulttocalculatetheresistanceduetopassiveearthpressureinthiscase.Itisnotnecessarilypossible todeterminewhether thepassiveearthpressureof theground reaches itsultimatevalue in response
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
to thepileheaddisplacement corresponding to the staticmaximum lateral resistanceof thepiles. When thesuperstructureisdisplaceduntilthepassiveearthpressurereachesthevalueobtainedusingCoulomb’sequation,thereisadangerofthepileundergoingbendingfailure.Therefore,whenconsideringinclusionofthepassiveearthpressureresistanceat thefrontof thisembeddedsection, itshallnotbeincludedincalculationswithoutadequateexaminationofthesefacts.
(3)Forstructuraltypesinwhichsettlementoffacilitiesiscontrolledbyemployingpilesasfrictionpiles,forexample,piled-raftfoundations,122)orsoftlandingmoundlessstructureswithpiles,therearecasesinwhichitisreasonabletoconsiderthebearingcapacityundertheslabbottom. In case of the performance verification of the facilities above, it is necessary to confirm sufficiently thebehaviorcharacteristicsofthefacilities.
(4)ProcedureofperformanceverificationforpilefoundationsItisgenerallypreferablethatperformanceverificationofpilefoundationsbeconductedbytheprocedureshowninFig. 2.4.21.
Type of pilesShape of pilesDimensions of pilesArrangement of piles
Assumptions :
Type of pilesShape of pilesDimensions of piles (diameter, wall thickness, and length)Arrangement of pilesNumber of pilesPile driving angle
Determination :
Estimation of bearing capacity of pilesLoading testsStatic bearing capacity formulas
Displacement of single pile
Ultimate bearing capacity of single pile
Allowable bearing capacity of single pile
Stress generated in piles
Displacement of pile group
Ultimate bearing capacity of pile group
Allowable bearing capacity of pile group
Stress generated in piles
Soil conditionsLoad conditions Allowable displacement
Economy
End
Axial bearing capacity Axial pulling forceHorizontal resistance Negative skin frictionBucklingJoint efficiencyVibration and earthquake
Fig. 2.4.21 Example of Procedure of Performance Verification Procedure
[2] Distance between Centers of Piles
Whendeterminingthedistancebetweenthecentersofpilestobedriven,theworkability,deformationbehaviorofsurroundingground,andbehaviorasapilegroupisnecessarytobetakenintoaccount.
[3] Performance Verification of Pile Foundations during Construction
(1)ExaminationofLoadsduringConstruction
① Inperformanceverificationofpiles,itispreferabletoexaminenotonlytheloadsactingaftercompletionofconstructionbutalsothoseduringtransportation,positioning,anddriving.
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② DrivingsuspensioncontrolbypiledrivingformulasPile driving formulas, designed to calculate the static maximum bearing capacity of piles from dynamicpenetrationresistance,aredifficulttomakegooduseinprinciple.Althoughestimationsofthestaticmaximumbearingcapacityusingpiledrivingformulashavetheadvantageofbeingverysimple,theproblemliesintheiraccuracy.InFig. 2.4.22 bySawaguchi,23)thestaticmaximumbearingcapacityobtainedfromthepiledrivingformulaforsteelpilesiscomparedwiththeresultsofloadingtestsinaformoftheratiooftheformertothelatter.Thefigurerevealsmajordiscrepancyanddispersionbetweenthetwo.Inclayeysoil,soilisdisturbedduringpiledrivingandskinfrictiontemporarilydecreases.Therefore,thestaticmaximumbearingcapacitycannotbeestimatedbypiledrivingformulas. Insandysoil,piledrivingformulasaresaidtobeinaccurateforestimatingthebearingcapacityoffrictionpiles. Thelimitsofapplicabilityofpiledrivingformulasarediscussedinreference24). Nevertheless,whendrivingalargenumberofpilesintoalmostidenticalground,piledrivingformulascanbeusedasareferenceforestimatingtherelativedifferencesinbearingcapacitypereachdrivenpile.Thus,theapplicationoftheseformulasshouldberestrictedtoconstructionmanagementpurposes. However,theymayalsobeusedasreferencetoconfirmvariationinthebearingcapacityofeachpileortofinishthedrivingofeachpilesothattheyareallgovernedbythesamecondition. Ithasbecomepossible toseparate theresistanceof thepileshaftandresistanceat theendof thepilebyperformingandynamicpileloadingtest;moreaccuratedrivingsuspensioncontrolcanbeexpectedthanbydependingsolelyonpiledrivingformulas.
10 20 40 60 100 200 400 600 1,000%
Hiley’s equationHiley’s equation
Weisbach’s equationWeisbach’s equation
Denmark’s equationDenmark’s equation
Smith’s equationSmith’s equation
Janbu’s equationJanbu’s equation
Fig. 2.4.22 Distribution of Results of Pile Driving Formulas and Loading Tests
(a) Hiley’sequationHiley’sequationisthemostcommonpiledrivingformulaandisexpressedbyequations(2.4.50)and(2.4.51).
(2.4.50)Energy required for penetration of pile
Impulsiveloss
Loss due to elasticdeformation of pile
Loss due to elasticdeformation of ground
Loss due to cushion
(2.4.51)
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where Rdu :ultimatepile-drivingresistance;i.e.,dynamicmaximumbearingcapacity(kN) WH :weightofhammer(kN) WP :weightofpileincludingpileheadattachments(kN) F :impactenergy(kJ) ef :efficiencyofhammer,rangingfrom0.6to1.0,dependingonthetypeofhammer126) e :reboundcoefficient(e =1ifcompletelyelastic,ande =0ifcompletelynon-elastic) S :finalsettlementofpile(m) C1 :elasticdeformationofpile(m) C2 :elasticdeformationofground(m) C3 :elasticdeformationofpileheadcushion(m)
MostpiledrivingformulasareobtainedbyreplacingC1,C2,C3,ef,e,etc.inequation(2.4.51)withappropriatevalues. Equation (2.4.52) is considered relativelywell-suited to steel piles. Assuming the impact betweenhammerandpiletobeelastic,i.e., e =1,thefollowingisderived:
(2.4.52)
ThetermC1+C2+C3intheaboveisthesumofelasticdeformationofground,pile,andpileheadcushion.
Ofthese,thetermC1+C2areequaltothereboundK measuredatthepileheadinpiledrivingtests(seeFig. 2.4.23).Withsteelpiles,elasticdeformationC1isdominant,whileC3isgenerallysmaller.Thus,ifC3isneglected,thefollowingcanbeassumed:
(2.4.53)
thus, (2.4.54)
where Rdu :dynamicmaximumbearingcapacityofpile(kN) ef :efficiencyofhammer,setat0.5incaseofequation(2.4.54) S :settlementofpile(m) drophammers:meansettlementperblowforthefinal5–10strikes(m) otherhammers:meansettlementperblowforthefinal10–20strikes(m) K :valueofrebound(m) F :impactenergy(kN·m) drophammer: Singleactionsteamhammer: F=WH H
doubleactionsteamhammer:F=(ap+WH )H dieselhammer: F=2 WH H H :dropheightofhammer(m) WH :weightofhammer(kN) a :cross-sectionalareaofcylinder(m2) p :steampressureorairpressure(kN/m2)
ThedesignvalueofaxialresistanceRdadisobtainedbymultiplyingRdubythepartialfactorγ.Here,apartialfactorγof0.33cangenerallybeused.
(2.4.55)
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PencilPencil
Metal clamp
Pile
Penetration of pile (s)
Elastic compression of pile and ground (K)
(a) (b)
Fig. 2.4.23 Rebound Measurement
[4] Joints of Piles
(1) Jointsofpilesshallbesufficientlysafeagainstactionsaftercompletionaswellasduringconstruction.
(2)Jointsshallbeplacedatthepositionwherethereisasufficientmarginincross-sectionalstrengthandrelativelyfreefromcorrosion.
(3)Dependingon thepositionof joints, the forcesactingon jointsaftercompletionofa structurearesometimesfarsmallerthanthestrengthofthepiles.However,considerationsshouldbetakentoensurethesafetyofjointsagainstthepile-drivingstressduringconstruction,loadincreasesinfuture,andunexpectedstressesarisingwithinthecrosssectionofjoints.
(4)PositionofJointsExecutionofjointpartsisnecessarilyaccompaniedbyworkattheconstructionsite.Therefore,unlikefabricationinafactory,supervisionofconstructionworktendstobeinadequate.Accordingly,inperformanceverificationofjoints,caredifferentfromthatforthepileproperisnecessary.Evenindeepsectionswhicharenotaffectedbybendingstressunderordinaryconditions,thereareexamplesofbucklingofpilesatjointsandatpointswherethepilewallthicknesschangesbelowajoint.Thus,adequateexaminationisnecessary. Indeterminingthepositionofjoints,itisnecessarytoselectthejointpositionbasedonagoodunderstandingofthejointstructure,consideringallofthefactorsofbending,shear,compression,andtension.Apositionwheretheflexuralmomentissmallshallbeselectedifthejointstructureisweakagainstbending,andapositionwhereshearissmallshallbeselectedifthestructureisweakagainstshear. Thedurabilityofjointsisconsideredtobesmallincomparisonwiththepile.Forexample,insteelpiles,variouskindsofcorrosioncontroltreatmentareconsideredtocauseareductionoffunctionsduetoweldingatthispart.Therefore,jointpositionswherecorrosionisslightshallbeselected,andinparticular,positionswhicharesubjecttorepeatedwettinganddryingduetochangingwaterlevelsshallbeavoided. The lengthallotted toelements inonepile isdeterminedby thepositionof joints. Limitations related totransportation,constructionequipment,andworkspacefactorsshallbeconsideredindeterminingthelengthoftheelement.Itisconsideredadvantageoustoreducethenumberofjointstotheminimumanduselongelementsasmuchaspossible.Giventhepresenttransportationconditions,themaximumlengthsthatcanbetransportedare13mbyroadand20mbyrail.
(5)JointsinSteelPilesInsteelpiles, arcwelded joints shouldgenerallybeused,as this is themost reliable typeof joint. However,becausegas-pressureweldingandothernewmethodsarebeingdeveloped,whensufficientsafetyisconfirmedbytheresponsibleengineerbasedonadequatestudybytesting,theseothermethodsmayalsobeused.
(6)WoodPileJointsItisnotpreferabletousethewoodenjointswhenhorizontalforceorpullingforcedoesnotact.
(7)ReinforcedConcretePileJointsandPrestressedConcretePileJointsWhenreinforcedconcretepileandprestressedconcretepileareused to thestructurewherehorizontal forceorpullingforceacts,jointstructurewhichhasbeenconfirmedwithhighreliabilityshallbeselected.
[5] Change of Plate Thickness or Material Type of Steel Pipe Piles
(1)Whenchangingplatethicknessormaterialtypeofsteelpipepiles,alldueconsiderationsshallbegiventotheworkabilityandthedistributionofsectionforceonpiles.
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(2)Thesectionforceofsteelpipepilesvarieswithdepth,generallydecreasingasthedepthbecomeslarge.Therefore,platethicknessormaterialtypeofsteelpipepilesissometimeschangedoverthetotallengthfromtheeconomicalpointofview.
(3)Whenchangingplatethicknessormaterialtypeofsteelpipepiles,thepositionofthechangeshouldbeatthedepthwherethesectionforcearisinginthepilesdoesnotincrease.Cautionisalsorequiredbecausesuchachangemaynotbeallowedifalargenegativeskinfrictionisactive.
(4)Jointingpileswithdifferentthicknessandmaterialtypeshouldbedonebyshopcircularwelding.TheshapeoftheweldedsectionshouldcomplywithJISA5525.
[6] Other Notes regarding Performance Verification
(1)SteelPiles
① RadialbucklingofsteelpipepilesWhenusingclosedendedpilesandwhenusingopenendedpilesfromwhichthesoilistoberemovedforfillingwithconcrete, if thewall thicknessof thepile is extremely thin relative to thepilediameterorpenetrationlengthisextremelylarge,thereisadangerofbucklingintheradialdirectionduetotheearthpressureandwaterpressureactingonthepilesurface.Therefore,cautionisnecessary. Theexternalpressureatwhichbucklingoccurswhenasteelpipeissubjectedtouniformexternalpressurecangenerallybeexpressedasshowninequation(2.4.56).
(2.4.56)
where pk :externalpressurecausingbuckling(kN/m2) E :modulusofelasticityofsteel(kN/m2)E=2.1x108kN/m2
v :Poisson’sratioofsteelv=0.3 t :wallthicknessofcylinder(mm) r :radiusofcylinder(mm)
② AxialbucklingofsteelpipepilesInsteelpipepileswhichhaveathinwallthicknessrelativetothepilediameter,asinlargediameterpiles,thereisadangeroflocalbucklingduetoaxialloading. Thereisnodangerthatbucklingwilloccurduringpiledrivingprovidedtheimpactstressislessthantheyieldstressofthesteelpile.134)KishidaandTakanoproposedequation (2.4.57) toexpresstheeffectofwallthicknessonyieldstress.
(2.4.57)
where σpy :yieldstressofsteelpileconsideringeffectofwallthickness(kN/m2) σy :yieldstressofsteelpileagainststaticload(kN/m2)
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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2.5 Settlement of Foundations2.5.1 Ground Stress
(1) Itispreferablethatthestressinducedinagroundduetoloadonafoundationisestimatedbyassumingthatthegroundisanelasticbody.However,foruniformlydistributedload,thestressinthegroundmaybeestimatedbysimplyassumingthatthestressdisperseslinearlywithdepth.
(2)Whena structurebuilton thegroundwhichhasa sufficientmarginof safety factoragainst shear failure, thestressdistributioninthegroundcanberationallyapproximatedbyassumingthegroundtobeanelasticbody.TheelasticsolutionobtainedbyBoussinesqiscommonlyusedincalculationofstressdistributioninaground.Boussinesq’ssolution isbasedonthecase thataverticalconcentrated loadactsonthesurfaceofanisotropicandhomogeneoussemi-infiniteelasticbody.Bysuperposingthissolution,itispossibletocalculatethestressdistributioninthegroundwhenalineloadorspatially-distributedloadactsonthegroundsurface.Inadditiontothiselasticsolution,theKoeglermethodthatassumesthestresstodisperselinearlywithdepthcanbeusedforestimatingthestressinthegroundwhenastriploadorarectangularloadactsontheground.137)
2.5.2 Immediate Settlement
(1) Inestimationofimmediatesettlement,itispreferabletoapplythetheoryofelasticitybyappropriatelysettingthemodulusofelasticityoftheground.
(2)Immediatesettlement,unlikeconsolidationsettlement,whichwillbedescribed in the following, iscausedbysheardeformationandoccurssimultaneouslywithloading.Becausesandygrounddoesnotundergolong-termconsolidationsettlementlikethatincohesivesoilground,immediatesettlementinsandyground,asdescribedhere, canbe considered tobe total settlement. On theotherhand, the immediate settlementof cohesive soilgroundisaphenomenonwhichiscausedbysettlementduetoundrainedsheardeformationandplasticflowinthelateraldirection.Insoftcohesivesoilground,therearecasesinwhichimmediatesettlementmaybeignoredinperformanceverificationbecauseitissmallerthantheconsolidationsettlementdescribedbelow. Incalculationsofimmediatesettlement,thegroundisusuallyassumedtobeanelasticbody,andthetheoryofelasticityandthemodulusofelasticityE andPoisson’sratiov areused.Asthemodulusofelasticityofsoilvariesgreatlydependingonthestrainlevel,itisimportanttomakecalculationsusingamodulusofelasticitythatcorrespondstotheactualstrainlevel.Forexample,thestraininsoftgroundwithasmallsafetyfactorisontheorderof0.5%to1.5%,whilethatinexcavationofhardgroundanddeformationoffoundationsisnomorethan0.1%.TherelationshipbetweenthestrainlevelandtheelasticmodulusshallfollowPart II,Chapter 3, 2.3.1 Elastic Constants.
2.5.3 Consolidation Settlement
(1)Settlementsoffoundationsthatarecausedbyconsolidationofgroundshallbeexaminedinaccordancewiththeproceduresdescribed inPart II, Chapter 3,2.3.2 Compression and Consolidation Characteristics. Designparametersforthegroundisnecessarytobedeterminedbyusinganappropriatemethodbasedontheresultsofconsolidationtests.
(2)Calculationsofsettlementsduetoconsolidationcanbeperformedbasedontheresultsofconsolidationtestsonundisturbed samplesof cohesive soils. Thefinal consolidation settlement,which is the amountof settlementwhenconsolidationcausedbyaloadhasfinallycompleted,isdeterminedbythecompressibilitypropertiesofthesoilskeleton,andcanbeestimateddirectlyfromtheresultsofconsolidationtests.Time-dependentchangesinsettlementuptothefinalconsolidationsettlementofafoundationarenecessarytobecalculatedbasedonthetheoryofconsolidation.
(3)CalculationMethodsofFinalConsolidationSettlementofFoundationFinalconsolidation settlementof foundationcanbecalculatedbyusing the followingequationsdescribed inPart II, Chapter 3,2.3.2 Compression and Consolidation Characteristics.
①Whenusinge-logp curve:
(2.5.1)
where S :finalconsolidationsettlementduetopressureincrementΔp(m) h :layerthickness(m) Δe :changeinvoidratioforpressureincrementΔp
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e0 :initialvoidratio
②WhenobtainedfromCc:Applicationofthismethodislimitedmainlytothecasesinwhichconsolidationofthenormalconsolidationareaisconsidered.
(2.5.2)
where S :finalconsolidationsettlementduetopressureincrementΔp(m) h :layerthickness(m) Cc :compressionindex e0 :initialvoidratio p0 :overburdenpressure(kN/m2) Δp :pressureincrement(kN/m2)
③ whenobtainedfrommv:Applicationofthismethodislimitedtocasesinwhichtheincrementofconsolidationpressureissufficientlysmallthatmvcanbeconsideredconstant.
(2.5.3)
where S :finalconsolidationsettlementduetopressureincrementΔp(m) mv :coefficientofvolumecompressibilitywhenconsolidationloadis (m2/kN) p0 :overburdenpressure(kN/m2) Δp :pressureincrement(kN/m2) h :layerthickness(m)
(4)CalculationMethodofTime-SettlementRelationshipTherateofconsolidationsettlementiscalculatedfromtherelationshipbetweentheaveragedegreeofconsolidationU andthe timefactorT that isobtainedfromTerzaghi’sconsolidation theory,where thedissipationofexcessporewaterpressureisexpressedasapartialdifferentialequationofthermalconductivitytype.Theamountofsettlements(t)atagiventimet canbecalculatedfromtheaveragedegreeofconsolidationU(t)bythefollowingequation:
(2.5.4)
Thefiniteelementanalysiswithvisco-elasto-plasticitymodelforcohesivesoilcanbeutilizedforaccurateanalysisoftheconsolidationsettlementthattakesaccountofinhomogeneityonconsolidationpropertiesoftheground,theeffectofselfweightofcohesivesoillayerandtime-relatedchangesinconsolidationload.
(5)DivisionofCohesiveSoilLayersubjecttoConsolidationWhen calculating the final consolidation settlement, the cohesive soil layer is usually divided into a numberofsub-layersasshowninFig. 2.5.1. Thisisbecausetheconsolidationpressureandthecoefficientofvolumecompressibilitymv varywithdepth.Withthemv method,thefinalconsolidationsettlementoffoundationmaybecalculatedusingequation(2.5.5).
(2.5.5)
where S0 :finalconsolidationsettlement(m) ∆σz :incrementsofconsolidationpressureatthecenterofasub-layer(kN/m2) mv :coefficientofvolumecompressibilityfortheconsolidationpressureatthecenterofeachsub-
layerequalto ,(m2/kN) whereσz0istheeffectiveoverburdenpressureatthecenterofasub-layerbeforeconsolidation ∆h :thicknessofasub-layerintheconsolidatedlayer(m)
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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mv1
mv
Z
ΔσZ
ΔσZ1
Δh1
Z Z
Z1
Z2
Fig. 2.5.1 Calculation of Consolidation Settlement
Sincemvand∆σzgenerallydecreasewithdepth,thecompressionineachsub-layerbecomessmallerasthedepthincreases.Thethicknessofsub-layerΔhisusuallysetat3to5m.ItshouldbenotedthattheconsolidationsettlementofsoftcohesivesoilwillbeunderestimatedwhenΔhistakentoolarge,becausethevalueofmνofthesurfacelayerisverylargeanditgovernsthetotalsettlement.Theincrementofconsolidationpressure∆σziscalculatedatthecenterofeachsub-layerusingtheverticalstressdistributionwithdepth,whichisdescribedin2.5.1 Ground Stress.Theterm∆σzistheincrementinverticalstressduetoloading.Inthenaturalground,itisusuallyassumedthatconsolidationduetotheexistingoverburdenpressurehascompletelyfinished. Althoughthedistributionofsubgradereactionatthebottomoffoundationisnotthesameasthatoftheactingloadduetotherigidityoffoundation,therigidfoundationsettlesunifomlyandthestressdistributionofsubsoilatacertaindepthbecomesirrelevanttothedistributionofreactionimmediatelybelowthefoundationbottom.
(6)VerticalCoefficientofConsolidationcv andHorizontalCoefficientofConsolidationchWhenporewaterofgroundflowsverticallyduringconsolidation,theverticalcoefficientofconsolidationcvisused.Butwhenverticaldrainsareinstalled,drainedwaterofgroundflowsmainlytothehorizontaldirectionandthehorizontalcoefficientofconsolidationchshouldbeused.ThevalueofchobtainedfromexperimentsontheclayinJapaneseportareasrangesfrom1.0to2.0timesthevalueofcv.140)However,inperformanceverificationch≒cvisacceptablewhenconsideringadecreaseinchduetodisturbancecausedbyinstallationofverticaldrains,inhomogeneousconsolidationpropertiesintheground,andothers.
(7)CoefficientofConsolidationcv ofOverconsolidatedClay141)Thecoefficientofconsolidationofcohesivesoilinovercosolidatedstateisgenerallylargerthanthatinnormallyconsolidatedstate. Whenthecohesivesoilseemstobeclearlyinoverconsolidatedstate,thevalueofcv usedforperformanceverificationshouldbetheoneatthemeanconsolidationpressurebetweentheexistingeffectiveoverburdenpressure and thefinalpressure after consolidation. However, rather than simplycalculatingcv atthemeanconsolidationpressure, itwouldbebetter todetermineaweightedmeanvalueofcv considering thesettlement.
(8)RateofConsolidationSettlementinInhomogeneousGroundWhen the ground consists of alternate layers with different cv values, the rate of consolidation settlement isanalyzedusingtheequivalent-thicknessmethod142)ornumericalanalysissuchasthefinitedifferencemethod143)or thefiniteelementmethod.144),145),146) Theequivalent-thicknessmethodisusedasasimplifiedmethod,butit sometimesyields significanterrors. When theground is inhomogenous toa largeextentorwhenaccurateestimationisrequired,itisrecommendedtousethefiniteelementmethod.
(9)SettlementduetoSecondaryConsolidationThe shape of the settlement - time curve in long-term consolidation tests on cohesive soil is consistentwithTerzaghi’sconsolidationtheoryuptothedegreeofconsolidationofaround80%.Whentheconsolidationpassesthislevel,thesettlementincreaseslinearlywithlogarithmoftime.Thisisduetothesecondaryconsolidationthat arises with the time-dependent properties of soil skeleton under consolidation load, beside the primaryconsolidationthatcausesthesettlementaccompanyingdissipationofexcessporewaterpressureinducedinthecohesivesoilduetoconsolidationload. Thesettlementduetosecondaryconsolidationisparticularlysignificantinpeatandotherorganicsoils.Inordinaryalluvialclaylayers,theconsolidationpressurecausedbyloadingisoftenseveraltimesgreaterthantheconsolidationyieldstressofthesubsoil.Undersuchconditions,thesettlementduetosecondaryconsolidationissmallerthanthatduetotheprimaryconsolidation,andisnotsignificantintheperformanceverification.Butwhentheconsolidationpressureactingonthegroundduetoloadingdoesnotgreatlyexceedconsolidationyieldstress,thesettlementduetosecondaryconsolidationtendstocontinueoveralongtime,eventhoughthesettlementduetoprimaryconsolidationmaybesmall.Inthiscase,thesecondaryconsolidationsettlementmustbefullytakenintoaccountintheperformanceverification.
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
Thesettlementduetosecondaryconsolidationmaybegenerallycalculatedusingthefollowingequation:
(2.5.6)
where Ss :settlementduetosecondaryconsolidation(m) Cα :coefficientofsecondarycompression t :time(d) t0 :starttimeofsecondaryconsolidation(d) h :claylayerthickness(m)
Thecoefficientofsecondarycompressionisobtainedfromconventionalconsolidationtests.ItcanalsobeestimatedfromtherelationshipbetweenandthecompressionindexCc thatisgenerallyexpressedinthefollowingequation147)
(2.5.7)
2.5.4 Lateral Displacement
(1) In quaywalls or seawalls constructed on soft cohesive ground, countermeasures are preferable when lateraldisplacementsduetosheardeformationofthegroundhaveanadverseeffectonstructures.
(2)Inquaywallsorseawallsonsoftground,therearecasesinwhichitisnecessarytoestimatelateraldisplacementscausedbysheardeformationoftheground.Lateraldisplacementsincludedisplacementaccompanyingimmediatesettlementoccurringimmediatelyafterloading,anddisplacementwhichoccurscontinuouslyovertimethereafter.In cases where the imposed load is significantly smaller than the ultimate resistance of the ground, lateraldisplacementaccompanyingimmediatesettlementcanbepredictedbyanalyzingthegroundasanelasticbody.
(3)Afrequentproblemwithsoftgroundislateraldisplacementsoccurringasacombinationofconsolidationandcreepdeformationduetoshearwhentheratiooftheresistanceofthegroundasawholetothemomentduetoactionsislow,beingontheorderof1.3.Amethodofpredictingwhetherthiskindoflateraldisplacementwilloccur or not using a simple constant based on past experience has been proposed.148)Whenmaking amoredetailed analysis, computer programswhich obtain changes over time in settlement and lateral displacementbyfiniteelementanalysisarewidelyused,applyinganelasto-plasticmodeloranelasto-viscoplasticmodel tocohesivesoilground.Becausetheimportanceoflateraldisplacementdiffersgreatlydependingonthefunctionsofthefacilities,itisnecessarytoselectanappropriatecalculationmethodconsideringthesefunctions.
2.5.5 Differential Settlements
(1)Whenconstructingstructuresonasoftcohesiveground,unevensettlementsofthegroundshallbetakenintoaccount and appropriate countermeasures are preferable when uneven settlements have an adverse effect onstructures.
(2)Asimplifiedmethodisproposedforestimatingunevensettlementinreclaimedlandinportareas.Thismethodclassifiesthegroundofreclaimedlandintothefollowingfourtypes;
① Extremelyinhomogeneousground② Inhomogeneousground③ Ordinaryground④ Homogeneousground
Fig. 2.5.2 showsthemeanunevensettlementratiosforeachtypeofground. Theunevensettlementratiomeanstheratioofthedifferenceintheaveragesettlementoccurringbetweentwoarbitrarypointstothetotalsettlement.Forexample,becausethemeanunevensettlementratiofortwopointsseparatedbyadistanceof50mingroundoftype(b)is0.11,whensettlementofxcmoccursfromacertainreferencetime,theaverageunevensettlementoccurringin thedistanceof50mcanbecalculatedas0.11x. Whenapplyingthismethodtoactualproblems,itispreferabletocorrectthevaluesinFig. 2.5.2forthereferencetimeandthedepthofthegroundwhichistheobjecttosettlement.150),151)
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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Extremely inhomogeneous ground Inhomogeneous groundOrdinary groundHomogeneous ground
Mea
n un
even
settl
emen
t rat
io
Distance between 2 points 0 20 50 100
0.5
0.4
0.3
0.2
0.1
0
Fig. 2.5.2 Relationship between Distance and Uneven Settlement Ratio in Reclaimed Land
References
1) ArchitecturalInstituteofJapan:Guidelinefordesignofarchitecturalfoundation,p.108,20012) Davis,E.H.andBooker:Theeffectofincreasingstrengthwithdepthonthebearingcapacityofclays,Geotechnique,Vol.23,
No,4,19733) Nakase,A.:Bearingcapacityofrectangularfootingsonclayofstrengthincreasinglinearlywithdepth,SoilandFoundations,
Vol.21,No.4,pp.101-108,19814) Yamaguchi,K.:SoilMechanics(FullyrevisedEdition),Chapter9Bearingstrength,Giho-doPublishing,pp.273-274,19855) Kobayashi,M.,M.Terashi,K.TakahashiandK.Nakajima:ANewMethodforCalculatingtheBearingCapacityofRubble
Mounds,Rept.ofPHRIVol.26,No.2,19876) Shoji,Y.:Studyon shearingPropertiesofRubbleswithLargeScaleTriaxialCompressionTest,Rept. ofPHRIVol.22,
No,4,19837) Minakami,J.andM.Kobayashi:SoilStrengthCharacteristicsofRubblebyLargeScaleTriaxialCompressionTest,Rept.of
PHRINo.699,19918) JapanRoadAssociation:Specificationsandcommentaryofhighwaybridges,PartIVSubstructures,pp.231-273,19969) RailwayTechnicalResearchInstitute:Designstandardsforrailwaystructuresandcommentary,Foundationstructures,Soil
pressureresistancestructure,pp.175-178,199710) A.W.Skempton:Thebearingcapacityofclays,Proc.BuildingResearchCongress,Div.1,pp.180-189,195111) G.G.Meyerhof:Theultimatebearingcapacityoffoundations,GeotechniqueVol.2,No,4,pp.301-332,195112) Takahashi,K.andM.Sawaguchi:ExperimentalStudyontheLateralResistanceofaWell,Rept.ofPHRIVol.16No.4,pp.3-
34,197713) Japan Geothechnical Society Edition: Vertical loading tests of Geothechnical Society’s Standard vertical pile, and
commentary-FirstrevisedEdition-,p.271,200214) Yamagata,K.andK.Nagai:Examinationofbearingstrengthofopenendsteelpiles(Part2),ProceedingsofArchitectural
InstituteofJapan,No.213,pp.39-44,197315) Kitajima,S.,S.Kakizaki,Y.HanakiandH.Tahara:OntheAxiallyBearingCapacityofSinglePiles,TechnicalNoteofPHRI
No.36,pp.1-66,196716) Japan Geothechnical Society Edition: Vertical loading tests of Geothechnical Society’s Standard vertical pile, and
commentary-FirstrevisedEdition17) Kusakabe,O.andT.Matumoto:Rapidloadingtesting(Stanamictest)methodandexamplesoftests,SoilandFoundation,Vol.
43,No.5,pp.19-21,199518) Katayama,T.,S.Nishimura,T.Wakiya,M.Hayashi,Y.YoshizawaandA.Shibata19) SocietyofSoilMechanicsandEngineeringScienceEdition:Designmethodforpilefoundationandcommentary,20) G.G.Meyerhof:Penetrationtestsandbearingcapacityofcohesionlesssoi1,Proc.A.S.C.E.,Vol.82,S.M.1,pp.1-10,195621) JapanRoadAssociation:Specificationsandcommentaryofhighwaybridges,PartIVSubstructures,pp.353-363,200222) RailwayTechnicalResearchInstitute:Designstandardsforrailwaystructuresandcommentary,Foundationtructures,Soil
pressureresistancestructure,SIUnitsversion,pp.227-232,2000
–480–
TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
23) ArchitecturalInstituteofJapan:Guidelinesforarchitecturalfoundation,pp.229-230,200124) Takahashi,K.:BehaviorofSinglePilesinSubsidingGround,Rept.ofPHRINo.533,p.17,198525) Yamaguchi,T.:SoilMechanics(FullyrevisedEdition),Giho-doPublishing,pp.281-282,198426) Yasuyuki, N., H. Ochiai and S. Oono: Practical evaluation equation of point bearing capacity of piles considering
compressibilityanditsapplication,SoilandFoundation,Vol.49,No.3,pp.12-15,2001.27) Ando,N.H.Ochiai andS.Ono:GeotechnicalEngineering estimationof vertical bearing capacity of piles applying in-
situtestsanditsapplication,JapanGeothechnicalSociety,Proceedingsof45thSymposiumonGeothecnicalEngineering,pp,163-167,2000.
28) JapanRoadAssociation:SpecificationsandCommentaryforHighwayBridges,PartIVSubstructures,MaruzenPublications,pp.333-363,2002
29) M.J.Tomilinson:FoundationDesign andConstruction,FifthEdition,Skin frictiononpile shaft,LongmanScientific&Technical,pp.415-419,1986
30) Yamahara,H.:Structuresofbearingcapacityofsteelpiles,SoilandFoundation,Vol.l7,No.11,pp.19-27,196931) Goto,H.andT.Katsumi:Fundamentalstudiesonsettlementsoflargediametersteelpiles,Jour.JSCENo.138,pp.1-10,196732) Aoki,M.andH.Kishida:Ultimateresistancecapacityofsandsfilledwithinopenendedpiles,Proceedingsof14thConference
ofSoilMechanics,pp.913-916,197933) Katsumi,T.andN.Kitani:Fundamentalstudiesiontheeffectofblockadeonopenpiles,Jour.JSCEVol.323,pp.133-139,
198234) Nishida,Y.,H.Ohta,T.MatsumotoandK.Kurihara:Bearingcapacitydurtopluggedsoilinopen-endedpipepiles,Jour.
JSCEVol.364/III-4,pp.219-227,198535) Nagai,O.:Examinationofblockageeffectofopenendedsteelpiles,ProceedingsofSoilMechanics,Vo1.26,No.2,pp.113-
120,198636) Komatu,M.,K.HijiguroandM.Tominaga:Someexperimentsonblockageoflargediametersteelpiles,SoilandFoundation,
Vol.17,No.5,pp.11-16,196937) Kishida,H.,Arihara andHara:Behavior of sandfilledwithin open endedpiles, Proceedings of 9thConferenceofSoil
Mechanics,pp.549-552,197438) JapanAssociationofSteelPipePiles:Steelpiles-designandconstruction-,p.110,200439) Kikuchi,Y.,H.Sasaki,H.Shimoji,Y.SaimuraandH.Yamashita:Verticalbearingcapacityof largediametersteelpile,
ProceedingsofStructuralEngineering,Vol.51A,2005.40) Kusakabe,O.,Y.KikuchiandJ.Fukui:PresentationsoftheresultsofloadingtestsofcoastalroadsofTokyoPort,Proceedings
of40thConferenceonGeotechnicalEngineering,pp.1669-1688,2005.41) ArchitecturalInstituteofJapan:Guidelinesforarchitecturalfoundation,pp.229-230,200142) JapanRoadAssociation:SpecificationsandCommentaryforHighwayBridges,PartIVSubstructures,MaruzenPublications,
pp.333-334,200243) RailwayTechnicalResearchInstitute:Designstandardsforrailwaystructuresandcommentary,Foundationstructures,Soil
pressureresistancestructure,SIUnitsversion,pp.227-232,200044) A.Kezdi:Bearingcapacityofpilesandpilegroups,Proc.,4th.Int.Conf.S.M.F.E.,Vol.2,pp.50-51,195745) K.Terzaghi,R.B.Peck,G.Mesri:SoilmechanicsinengineeringpracticeThirdEdition,JohnWiley,pp.435-436,199546) R.B.Peck,W.E.Hanson,T.H.Thornburn:Foundationengineering,JohnWiley,pp.260,195347) Takahashi,K.:BehaviorofSinglePilesinSubsidingGround,Rept.ofPHRINo.533,pp.8-11,198548) ArchitectualInstituteofJapan:Guidelinesforarchitecturalfoundation,pp.229-230,200149) Takahashi,K.:BehaviorofSinglePilesinSubsidingGround,Rept.ofPHRINo.533,pp.41-50,198550) Sawaguchi,M.:ApproximateCalculationofNegativeSkinFrictionofaPile,Rept.ofPHRIVol.10,No.3,pp.67-87,197151) Takahashi,K.:BehaviorofSinglePilesinSubsidingGround,Rept.ofPHRINo.533,pp.92-168,198552) ArchitecturalInstituteofJapan:Guidelinesforarchitecturalfoundation,pp.156-163,200153) Yokoyama,Y.:Calculationmethodsofpilestructuresandsamplecalculations,Sankai-doPublishing,pp.147-152,197754) Nakase,A.,T.OkumuraandM.Sawaguchi:Easy-to-understandFoundationworks,KajimaPublishing,p53,199555) R.D.Chellis:Pilefoundations,McGrawHill,p.464,1961R.D.Che1Hs:Pilefbundations,McGrawHil1,p.464,196156) K.Terzaghi,R.B.Peck,G.Mesri:SoilmechanicsinengineeringpracticeThirdEdition,JohnWiley,pp.436-444,199557) R.B.Peck,W.E.Hanson,T.H.Thornburn:Foundationengineering,JohnWiley,pp.238-239,pp.273-275,195358) G.P.Tschebotarioff:Foundations,retainingandearthstructuresSecondEdition,McGraw-Hill,pp.217-262,197359) W.C.Teng:Foundationdesign,Prentice-Hall,pp.220-222,196260) A.L.Little:Foundations,Arnold,pp.174-179,196161) H.O.Ireland:Pullingtestsonpilesinsand,Proc.4thInt.Conf.S.M.F.E.,Vol.2,p.45,195762) ArchitecturalInstituteofJapan:Standardsandcommentaryforarchitecturalsteelpilefoundation,p.55,196363) Kubo,K.:ANewMethodfortheEstimationofLateralResistanceofPile,Rept.PHRIVol.2,No.3,p.2,196464) Yokoyama,Y.:Designofsteelpilesandconstruction,Sankai-doPublishing,pp.188-196,196365) Takeshita,J.:Calculationofgrouppiles,CivilEngineeringTechnology,Vol.19,No.8,pp.54-60,1964,No.9,pp.75-80,1964,
No.10,pp.71-79,196466) Fujiwara,T.andK.Kubo:Experimentalstudyonlateralbearingcapacityofpiles(Part1),TechnicalResearchInstituteof
Transport,Vol.11,No.6,pp.41-53,1961
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
–481–
67) Kubo.K.:Experimentalstudyonlateralbearingcapacityofpiles(Part3),TechnicalResearchInstituteofTransport,Vol.12,No.2,pp.49-50,1962
68) Kubo,K.:ANewMethodfortheEstimationofLateralResistanceofPile,Rept.PHRIVol.2,No.3,pp.1-372,196469) Y.L.Chang:Lateralpileloadingtests,Trans.,A.S.C.E,Vol.102,pp.273-276,193770) PHRI,YawasaSteel:StudyonhorizontalresistanceofH-shapedpiles,pp.345-353,196371) Kubo,K.:ANewMethodfortheEstimationofLateralResistanceofPile,Rept.PHRIVol.2,No.3,pp..6-8,196472) Kubo.K.:Experimentalstudyonlateralbearingcapacityofpiles(Part2),TechnicalResearchInstituteofTransport,Vol.11,
No.12,p.550,196273) Kubo.K.:Experimentalstudyonlateralbearingcapacityofpiles(Part2),TechnicalResearchInstituteofTransport,Vol.11,
No.12,p.550,196274) Sawaguchi,M.:SoilConstantsforPiles,Rept.ofPHRIVol.7,No.2,p.87,196875) Yamashita,I.,T.Inatomi,K.OguraandY.Okuyama76) Yamashita,I.,T.Inatomi,K.OguraandY.Okuyama77) Kubo,K.:ANewMethodfortheEstimationofLateralResistanceofPile,Rept.PHRIVol.2,No.3,pp.14-15,196478) Fujiwara,T.andK.Kubo:Experimentalstudyonlateralbearingcapacityofpiles(Part1),ReportofTechnicalResearch
InstituteofTransport,Vol.11,No.6,pp.61,196179) Sawaguchi,M.:SoilConstantsforPiles,Rept.OfPHRIVol.7,No.2,PP.82-83,196880) Kubo.K.:Experimentalstudyonlateralbearingcapacityofpiles(Part3),ReportofTechnicalResearchInstituteofTransport,
Vol.12,No.2,P.190,196281) Kikuchi,Y.,K.AbeandK.Yuasa*Changeincharacteristicsoflateralresistanceofbutteredpileduetotheimprovementby
sandcompactionpile,Proceedingsof34thConferenceonGeotechnicalEngineering,pp.1661-1662,199982) K.Terauchi,T.Sato,M.Sawaguchi,Y.Kikuchi,S.Kitazawa,M.lmai:Effectoflateralresistanceofcoupledpilesonthefield
loadingtest,CoastalGeotechnicalEngineeringinPractice,pp.375-380,200083) Yokoyama,Y.:Calculationmethodsofpilestructuresandsamplecalculations,Sankai-doPublishing,pp.32-47,197784) Yokoyama,Y.:Calculationmethodsofpilestructuresandsamplecalculations,Sankai-doPublishing,p.68,197785) Yokoyama,Y.:Calculationmethodofpilestructuresandsamplecalculations,Sankai-doPublishing,pp.47-68,197786) K.Terzaghi:Evaluationofcoefficientofsubgradereaction,Geotechnique,Vol.5,No.4,pp.316-319,195587) Yokoyama,Y.:Calculationmethodofpilestructuresandsamplecalculations,Sankai-doPublishing,pp.139-141,197788) Yokoyama,Y.:Calculationmethodofpilestructuresandsamplecalculations,Sankai-doPublishing,pp72,197789) Kikuchi,Y.andM.Suzuki:Varianceofthesubgradereactionfortheestimatingtheresistanceofapileperpendiculartopile
axis,ASCEGSPinnovativeMethodsforFoundationAnalysisandDesignforGeoshanghai2006,pp.111-118,2006,90) Kikuchi,Y.andM.Suzuki:Aproposalonevaluationmethodofcoefficientofsubgradereactioninthelateraldirectionto
pileaxis,Proceedingsof41stConferenceonGeotechnicalEngineering,PP.1489-1490,200691) Sawaguchi,M.:SoilConstantsforPiles,Rept.OfPHRIVol.7,No.2,pp.21-25,196892) Y.L.Chang:Lateralpileloadingtests,Trans.,A.S.C.E,Vol.102,pp.50-54,193793) JapanRoadAssociation:SpecificationsandCommentaryforHighwayBridges,PartIVSubstructures,MaruzenPublications,
pp.239-241,200294) Takahashi,K.andY.Shoji:ExperimentalStudyonVerticalAnchorPilesofSheetPileWall,Rept.ofPHRIVol.22,No.4,
pp.33-58,198395) Shoji,Y.:ExperimentalStudyonLateralResistanceofaPilewithEmbeddedHeadinSand,Rept.ofPHRIVol.23,No.2,pp.
75-179,198496) Yokoyama,Y.:Designofsteelpilesandconstruction,Sankai-doPublishing,pp.148-157,196397) Yokoyama,Y.:Calculationmethodofpilestructuresandsamplecalculations,Sankai-doPublishing,pp.56-68,197798) Tanigawa,M.,M.SawaguchiandM.Tanaka:Horizontalbearingcapacityofpilesincompositeground-Replacementratio
ofclayeysoulbysandpileandCoefficientofsubgradehorizontalreaction-,Proceedingsof28thConferenceonGeotechnicalEngineering,pp.1599-1600,1993
99) Kitazume,M.andK.Murakami:BehaviourofSheetPileWallsintheImprovedGroundbySandCompactionPilesofLowReplacementAreaRatio,Rept.ofPHRIVol.32,No.2,pp.183-211,1993
100) Takahashi,K.andK.Iki:LateralResistanceofaPileinRubbleMound,Rept.ofPHRIVol.30,No.2,pp.229-273,1991101) Kikuchi,y.,M.Ishimaru:Coefficientsubgradelateralreactionofrubbleground,Proceedingsof53rdAnnualConferenceof
JSCE,3B,pp.52-53,1998102) Kubo,K:.LateralResistanceofShortPiles,Rept.ofPHRIVol.5,No.13,pp.1-38,1966103) Miyamoto,M.andM.Sawaguchi:GroupActiononLateralResistanceofPiles(1stReport)-SpacingEffectintheDirection
ofLoading-,Rept.ofPHRIVol.10,No.4,pp.53-108,1971104) B.B.Broms:Lateralresistanceofpilesincohesionlesssoils,Proc.,ASCE,Vol.90,No.SM3,PP.123-156,1964105) Kikuchi,T.,T.Kamii,Y.MoriandS.Kagaya:Horizontalbearingcapacityofgrouppilesandthespacing,Proceedingsof
6thConferenceonSoilMechanics,pp.427-430,1971106) Tamaki,O.,K.MituhashiandT.Imai:Studyofgrouppileeffectsonhorizontalbearingcapacity,ProceedingsofJACE,192,
pp.79-89,1971107) Prakash,S.andSaran,D.:Behavioroflaterally-loadedpilesincohesivesoils,Proc.,3rdAsianConf.ofSoilMech.,pp.235-
238,1967
–482–
TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
108) Poulos,H.G.:Behavioroflaterally-loadedpiles,II-pilegroups,Proc.,A.S.C.E.,Vol.97,No.SM5.,1971,pp.733751109) JapanRoadAssociation:SpecificationsandCommentaryforHighwayBridges,PartIVSustructures,MaruzenPublications,
pp.245,2002110) Segawa,M.,T.UchidaandT.Katayama:DesginofCoupledBatterPiles(Part2)-TwoBatter,TechnicalNoteofPHRINo.
110,pp.1-14,1970111) M.Sawaguchi:Experimentalinvestigationonthehorizontalresistanceofcoupledpiles,Rept.PHRIVo1.9,No.1,pp.11-13,
1970112) Yokoyama,Y.:Calculationmethodsofpilestructuresandsamplecalculations,Sankai-doPublishing,pp.193-197,1977113) Aoki,Y.:Designofgrouppilesagainsthorizontalforce,SoilandFoundation,Vol.18,No.8,pp.27-32,1970114) Kikuchi,Y.,K.TakahashiandM.Suzuki:ExperimentalStudyonPeople’sSafetyagainstOvertoppingWavesonBreakwaters-
AstudyonAmenity-orientedPortStructures(2ndRept.)-,Rept.ofPHRIVol.31No.4,pp.33-60,1992115) Shinohara,T.andK.Kubo:Experimentalstudyonlateralbearingcapacityofpiles(Part1),TechnicalResearchInstituteof
Transport,Vol.11,No.6,pp.50-53,1961116) Kikuchi,Y.,K.TakahashiandT.Hirohashi:LateralLoadTestsonPiledSlabStructures,TechnicalNoteofPHRINo.773,
p.25,1994117) Kubo,K.andF.Saegusa:Reciprocalloadingtestofmodelpiles,Proceedingsof2ndStudyPresentationConferenceofPHRI,
pp.64-73,1964118) Kikuchi,Y.:LateralResistanceofsoftlandingmoundlessstructurewithpiles,TechnicalNoteofPARINo.1039,2003119) Kubo.K.:Experimentalstudyonlateralbearingcapacityofpiles(Part3),TechnicalResearchInstituteofTransport,Vol.12,
No.2,pp.181-205,1962120) Suzuki,A.,K.KuboandY.Tanaka:Lateralresistanceofverticalpilesembeddedinsandylayerwithslopingsurface,Rept.
ofPHRIVol.5,No.2,pp.1-20,1966121) BureauofPortandHarboursEdition:Handbookofcountermeasurestorequifactionofreclaimedarea,CoastalDevelopment
InstituteofTechnology,pp.314-319,1997122) JapanGeothechnicalSocietyEdition:Survey,design,constructionandinspectionofpilefoundation,pp.343-461,2004123) Sawaguchi,M.:Comparisonofcalculationresultsbyvariousestimationmethodsofdynamicbearingcapacities,Proceedings
of38thConferenceofJSCE,PartIII,pp.605-606,1983124) Heutker,T.(TranslatedbyM.Kishida):Shokoku-shaPublishing,pp.37-41,1978125) JapanRoadAssociation:SpecificationsandCommentaryforHighwayBridges,PartIVSubstructures,MaruzenPublications,
pp.509-510,2002126)R.D.Chellis:Pilefoundations,McGrawHill,p.464,1961R.D.Che1Hs:Pilefbundations,McGrawHil1,29-32,1961127)ArchitectualInstituteofJapan:Standardsandcommentaryforarchitecturalsteelpilefoundation,pp.31-32,1963128) JapanRoadAssociation:Specificationsandcommentaryofhighwaybridges,PartIVSubstructures,pp.353-363,2002129) Uto,K.,M.FuyukiandM.Sakurai:Reviewofmonitoringformulaeofpiledrivingdepth,Proceedingsof17thConference
onSoilMechanics,pp.2041-2044,1982130) Yokoyama,Y.:Designofsteelpilesandconstruction,Sankai-doPublishing,pp.188-196,1963131) Kato,T.:Experiment on plastic local buckling of steel pipe piles, Proceedings ofTechnicalConference ofArchitectual
InstituteofJapan:,pp.463-464,1971132) Kishida,H.andA.Takan:Bucklingofsteelpipepilesandreinforcementoftheend,ProceedingsofTechnicalConferenceof
ArchitectualInstituteofJapan:,No.213,pp.29-38,1973133) Suzunai,K.:Studyondeformationofsteelpileheadduetopiledrivingloads,ReportofTechnicalResearchInstituteof
Transport,Vol.12,No.2,pp.57-83,1962134) Yokoyama,Y.:Designandconstructionofsteelpiles,Sankai-doPublishing,pp.2351963135) JapanRoadAssociation:Specificationsandcommentaryofhighwaybridges,PartIVSubstructures,pp.353-363,2002136)ArchitectualInstituteofJapan:Guidelinefordesignofarchitecturalfoundation,2001137) Akai,K.:BearingCapacityandsettlementofsoil,Sankai-doPublishing,1964138) Ishii,Y.:TschbotarioffSoilMechanics,(Vil.1)Gihoi-doPublishing,p.212,1957139) J.O.Osterburg:Influencevaluesforverticalstressesinasemi-infinitemassduetoanembankmentloading,Proc.4th.Int.
Conf.S.M.F.E.,Vol.2,1957140) Kobayashi,M.,J.MinakamiandT.Tsuchida:DeterminationoftheHorizontalCoefficientofConsolidationcohesivesoil,
Rept.ofPHRIVol.29,No.2,1990141) Nakase,A.,M.KobayashiandA.Kanechika:ConsolidationParametersofOverconsolidatedClays,Rept.ofPHRIVol.12,
No.1,pp.123-139,1973142) L.A.PalmerandP.P.Brown:Settlementanalysisforareasofcontinuingsubsidence,Proc.4th.Int.Conf.S.M.F.E,Vol.1,
pp.395-398,1957143) R.L.SchifflnanandR.E.Gibson:Consolidationofnonhomogeneousclaylayers,JournalofS.M.F.E.,ASCE,Vol.90,No.SM
5,pp.1-30,1964144) Kobayashi,M.:NumericalAnalysisofOne-DimensionalConsolidationProblems,Rept.ofPHRIVol.21,No.1,1982145) Kobayashi,M.:Studyon theapplicationofFiniteElementMethodtosettlementanalysis,TokyoInstituteofTechnology
Dissertation,TechnicalNoteofSoilMechanicsLaboratory,No.1,1990146)Kobayashi,M.:FiniteElementAnalysisoftheEffectivenessofSandDrains,Rept.ofPHRIVol.30,No.2,1991
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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147) Mesri,G.:Coefficientofsecondarycompression,Proc.A.S.C.E,Vol.99,SM1,pp.123-137,1973148) Kasugai,Y.,K.MinamiandH.Tanaka:ThePredictionoftheLateralFlowofPortandHarbourStructures,TechnicalNote
ofPHRINo.726,1992149) Okumura,T.andT.Tsuchida:PredictionofDifferentialSettlementwithSpecialReferencetoVariabilityofSoilParameters,
Rept.ofPHRIVol.20,No.3,1981150) Tsuchida,T.andK.Ono:EvaluationofDifferentialSettlementswithNumericalSimulationandItsApplicationtoAirport
PavementDesign,Rept.ofPHRIVol.27,No.4,1988151) Tsuchida,T.:Estimationofdifferentialsettlementinreclaimedland,ProceedingsofAnnualConferenceofPHRI,1989
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
3 Stability of Slopes3.1 General
(1)Stability of slopes against slip failure caused by selfweight of soil or surchargemay be analyzed as a two-dimensionalproblem,assumingacirculararcslipsurfaceorastraightslidingsurface.
(2)Itisnecessarytoperformslopestabilityanalysisforthecaseinwhichaslopebecomesleaststable.
(3)Inslopestabilityanalysis,incaseswherethestabilityofthesoilmasscomprisingaslopeisreducedbytheselfweightofthesoilorsurcharge,astheultimateequilibriumstate,itisnecessarytoconfirmthatthedesignvalueofshearingresistanceexceedsthedesignvalueofshearingforcebasedonactions.Calculationmethodsusedintheslopestabilityanalysiscanalsobeusedtocalculatethebearingcapacityoffoundations,inadditiontothestabilityofslopes,asthesecalculationmethodsareusedtoexaminethestabilityofsoilmasses.ThemethoddescribedbelowcanbeusedinverificationofstabilityagainstvariablesituationsinrespectofLevel1earthquakegroundmotioninadditiontothePermanentsituation.
(4)ShapesofSlipSurface
① TypesofshapesofslipsurfacesTheoretically,shapesofslipsurfacesinslopestabilityanalysisarecombinationsoflinear,logarithmicspiral,and/orcirculararcshapes1).Inpractice,however,linearorcirculararcslipsurfacesareassumed.Whenthereisaparticularlyweaklayerandaslipsurfaceisexpectedtopassoverit,thatslipsurfaceorotherappropriateslipsurfacesmaysometimesbeassumed.Anassumedslipsurfaceingeneralshouldbetheonealongwhichtheslipofthesoilmasssmoothlytakesplace.Thus,aslipsurfacewithsharpbendsorcurvesthatseemstobekinematicallyunnaturalshouldnotbeused.
② SlipfailureofslopeonsandysoilgroundSlipfailureofslopesofdrysandorsaturatedsandusuallytakesaforminwhichtheslopecollapses,andasa result, its inclinationdecreases. Therefore, it ismore appropriate to consider a slopeof these types as astraightslidingsurface thanasacircularslipfailuresurface. Evenwhenconsideringacircularslipfailuresurface,theformisclosetoastraightlinepassingthroughthevicinityofthesurfacelayer.Theinclinationofasandyslopewhentheslopeisinastateofequilibriumistermedtheangleofrepose.Thisangleofreposeisequivalenttotheangleofshearresistance,whichcorrespondstothevoidratioofthesandcomprisingtheslope.Inthecaseofunsaturatedsand,theslopepossessesapparentcohesionresistancecausedbythesuctionduetothesurfacetensionofthewaterinthesand.Asaresult,itsangleofreposeisfarlargerthaninthecasesofdrysandandsaturatedsand.However,saturationmayincreaseduetoinfiltrationofrainwaterorariseinthegroundwaterlevel,causingasuddendecreaseinapparentcohesionresistance,orangleofrepose.Therefore,adequateconsiderationisnecessary.
③ SlopefailureofcohesivesoilgroundTheactualslipfailuresurfaceofcohesivesoilgroundisclosetoacirculararc,andadeepslipcalledthebasefailureoftentakesplace,whileashallowslipappearsnearthesurfacelayerinsandyslope. Slopestabilityanalysis isusually treatedasa two-dimensionalproblem. Althoughactualslipsurface inslopeswith longextention takes theformof three-dimensionalcurvedsurfaces,a twodimensionalanalysisgivesasolutionon thesaferside. When thestability isexpected todecreasedue tosurchargeoverafiniteextention,however,theresistanceofbothsidesofacylindricalfailuresurfacemaybetakenintoaccount.
(5)ActionsinSlopeStabilityAnalysisImportant causes of slip failures are selfweight of soil, surcharge,water pressure and others. Beside them,repeatedactionssuchasseismicforce,waveforce,andothersmaybeincluded.Resistanceagainsttheslipisgivenbyshearresistanceofsoilandcounterweight.Becausetheshearstrengthofsoilisrelatedwithtime,thestabilityproblemsonsoilmassareclassifiedintotwocases;loadingonthegroundinnormallyconsolidatedstate,andunloadingbyexcavation.Theformerisreferredtoasashort-periodstabilityproblemandthelatteralong-period.Itispreferabletouseshearstrengthappropriatetoeachcase(seePart II, Chapter 3, 2.3.3 Shear Characteristics).
(6)Stability verification in slope stability problems can be performed by confirming that the ratio of the shearstrength of soil to the shear stress in an assumed slip surface is greater than1.0. Thevalue of the obtainedratiowilldifferdependingontheassumedslipsurface.However,theresultwiththesmallestratioof“shearingresistance”/”shearing force” among the shearing resistance and shearing forceobtained assuming several slipsurfacesbasedonthegivenconditionsshallberegardedasthelimitstateforslipfailureoftheslopeunderstudy.
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(7)PartialFactorsInexaminationofthestabilityofslopes,thepartialfactorsforeachstructuraltypeoffacilitiesorpartialfactorsbytypeofimprovedsoilcangenerallybeused.Inperformanceverificationofstructuraltypesandembankmentsforwhichnopartialfactorsareparticularlyspecified,thevaluesshowninthissectioncanbeused.ThepartstobereferencedonpartialfactorsareasshowninTable 3.1.1.Becausethepositionoftheslipsurfacewilldifferdependingonhowthepartialfactorsforthesoilparameterandtheanalysismethodaredetermined,cautionisnecessarywhentherangeofsoilimprovementistobedeterminedbasedonthestabilityverification.Forexample,ifthepartialfactorofthesoilparameteroftheresistancesideissetsmall,therangeofslipfailure,whichisthelimitstate,willbenarrow.Thismeansthatthenecessaryrangeofsoilimprovementwillbeunderestimated.
Table 3.1.1 Parts to be Referenced on Partial Factors for Use in Verification of Slip Failure
Applicablefacilitiesforpartialfactors Partstobereferenced Applicablefacilities
Compositebreakwater Chapter 4 Protective Facilities for Harbors3.1 Gravity-type Breakwaters (Composite Breakwaters), Table 3.1.1
Uprightbreakwater,slopingcaissonbreakwater,uprightwave-dissipatingblocktypebreakwater,wave-dissipatingcaissontypebreakwater
Breakwaterarmoredwithwave-dissipatingblocks
Chapter 4 Protective Facilities for Harbors3.4 Gravity-type Breakwaters (Breakwaters Covered with Wave-dissipating Blocks), Table 3.4.1
Slopingtopcaissonbreakwaterarmoredwithwave-dissipatingblocks
Gravity-typequaywall Chapter 5 Mooring Facilities2.2 Gravity-type Quaywalls, Table 2.2.2
Gravity-typerevetment,placement-typecellular-bulkheadquaywall
Sheetpilequaywall Chapter 5 Mooring Facilities2.3 Sheet Pile Quaywalls, Table 2.3.3
Sheetpilerevetment,cantileveredsheetpilequaywall
SCPimprovedsoil Chapter 2, 4 Soil Improvement Methods4.10 Sand Compaction Pile Method for Cohesive Soil Ground, Table 4.10.2
Gravity-typequaywallorsheetpilequaywallapplyingSCPimprovement
Others Inaccordancewiththissection(3 Stability of Slopes)
Slopingbreakwaterandothersimilarfacilities
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
3.2 Examination of Stability3.2.1 Stability Analysis by Circular Slip Failure Surface
(1)ExaminationofthestabilityofslopescanbeperformedbycircularslipfailureanalysiswiththemodifiedFelleniusmethod,whichisgivenbythefollowingequation,orbyanappropriatemethodequivalenttothebearingforcein2.2.5 Bearing Capacity for Eccentric and Inclined Actions,dependingonthecharacteristicsoftheground.Inequation(3.2.1),thepartialfactorγafortheanalysismethodshouldbeanappropriatevaluecorrespondingtothecharacteristicsofthegroundandcharacteristicsofthefacilities.Ingeneral,γacanbesetat1.30orhigherforpermanentsituations,butincaseswherethereliabilityoftheconstantsusedinverificationcanbeconsideredhighbasedonactualdataforthesameground,andincaseswheremonitoringworkiscarriedoutbyobservingthedisplacementandstressofthegroundduringconstruction,valuesfromoflargerthan1.10andlessthan1.30canbeused.2)Incaseswherepartialfactorsaregivenforthestructuraltypeofthefacilitiesorbytypeofimprovedsoil,asshownin3.1(7) Partial Factors,thepartialfactorsgivenattheobjectivepartsshallbeused.
(3.2.1)
where R :radiusofcircularslipfailure(m) cd :incaseofcohesionsoilground,designvalueofundrainedshearstrength,andincaseofsandy
ground,designvalueofapparentcohesionindrainedcondition(kN/m2) l :lengthofbottomofslicesegment(m) W’d :design value of effective weight of slice segment per unit of length (weight of soil.When
submerged,unitweightinwater)(kN/m) qd :designvalueofverticalactionfromtopofslicesegment(kN/m) θ :angleofbottomofslicesegmenttohorizontal(º) φd :incaseofcohesionsoilground,0,andincaseofsandyground,designvalueofangleofshear
resistanceindrainedcondition(º) Wd :designvalueoftotalweightofslicesegmentperunitoflength,totalweightofsoilandwater
(kN/m) x :horizontaldistancebetweencenterofgravityofslicesegmentandcenterofcircularslipfailure
(m) PHd :designvalueofhorizontalactiononsoilmassofslicesegmentincircularslip(kN/m) a :lengthofarmfromcenterofcircularslipfailureatpositionofactionofPHd(m) S :widthofslicesegment(m) γa :partialfactorforanalysismethod
The design values in equation (3.2.1) can be calculated using the following equation bymultiplying thecharacteristicvaluebythepartialfactor.Ifpartialfactorsarenotparticularlydesignated,1.00canbeusedforallpartialfactorsinequation (3.2.2).
cd =γc ck ,W'd =γW' W'k ,qd =γq qk ,φd =tan–1(γtanφ tanφk),PHd =γPH PHk (3.2.2)
(2)Inslopestabilityanalysis,thecausesofslipfailureincludetheselfweightofthesoil,surcharge,waterpressure,wavepressure,andactionduetogroundmotion.Elementswhichresistslipfailureincludetheshearingresistanceofthesoilandcounterweight.Verificationofsafetyagainstslipfailureofslopesisperformedassumingthattheshearingresistanceofthesoilexceedstheshearingforceintheassumedslipsurface.Whenassumingacircularslipfailuresurface,thisisequivalenttoverifyingthatthemomentswhichworktoresistslipexceedthemomentswhichcauseslipforthecenterofthecircle.
(3)Intheslicemethodusedincircularslipfailuresurfaces,thesoilmassinsidetheslipcircleisdividedintoanumberofslicesbyverticalplanes,theshearingforceatthebottomsurfaceofeachsliceandtheresistantstressofthesoilarecalculatedconsideringthebalanceofforcesineachslice.Thefactthatthedesignvalueoftheshearingresistanceobtainedbyaddingthestressesforalloftheslicesexceedsthedesignvalueoftheshearingforcealongthesliplineisthenverified.Inordertosolvetheinter-slicebalanceofforcesintheslicemethod,itisnecessarytoassumestaticallythedeterminateconditions.Variousmethodshavebeenproposed,whichvarydependingontheassumptionsused.Ingeneral,themodifiedFelleniusmethodandthesimplifiedBishopmethodareused.
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(4)StabilityAnalysisMethodusingModifiedFelleniusMethod1),3),4)Variouscalculationmethodshavebeenproposedfortheslicemethod,dependingonhowtheforcesactingontheverticalplanesbetweentheslicesareassumed.ThemodifiedFelleniusmethodassumesthatthedirectionoftheresultantforceactingonverticalplanesbetweenslicesisparalleltothebaseoftheslices.ThismethodisalsoreferredtoasthesimplifiedmethodorTschbotarioffmethod.WhenacirculararcandasliceareasshowninFig. 3.2.1,equation(3.2.1)accordingtothemodifiedFelleniusmethodisapplicable. Inperformingslopestabilityanalysis,first,thecenteroftheslipcircleisassumed.Oftheslipcirclesthattakethispointastheircenter,theonewiththesmallestratioexpressedby“thedesignvalueofshearingresistance”/”designvalueofshearingforcebasedonloading”isobtained,anditsvalueisusedastheminimumratioforthatcenterpoint.Theminimumratioof“designvalueofshearingresistance”/”designvalueofshearingforce”forothercenterpointsisthenobtainedbythesamemethod.Verificationcanbeperformedforthelimitstateforslipfailureoftheslopeusingtheminimumvalueoftheminimumratiosobtainedbythecontourfortheminimumratios.
Fig.3.2.1 Circular Slip Failure Analysis using Modified Fellenius Method
(5)StabilityAnalysisbyBishopMethod3),5) Bishop5)proposesanequationwhichconsiderstheverticalshearingforceandhorizontalforceactingintheverticalplaneofaslice. Inactualcalculations,acalculationmethodwhichassumesthattheverticalshearingforcesareinbalanceisoftenused.ThismethodiscalledthesimplifiedBishopmethod.InthesimplifiedBishopmethod,γFfFfiscalculatedbasedonequation(3.2.3),5)andstabilitycanbeverifiedbytheverificationparameterFf≥1. In this equation, the symbolγ is thepartial factor for its subscript, and the subscriptsk andd are thecharacteristicvalueanddesignvalue,respectively.
(3.2.3)
where Ff :verificationparameter γFf :partialfactorforanalysismethod cd :incaseofcohesionsoilground,designvalueofundrainedshearstrength,andincaseofsandy
ground,designvalueofapparentcohesionindrainedcondition(kN/m2) S :widthofslicesegment(m) W’d :design value of effectiveweight of slice segment per unit of length (weight of soil. When
submerged,unitweightinwater)(kN/m) ød :incaseofcohesionsoilground,0,andincaseofsandyground,designvalueofangleofshear
resistanceindrainedcondition(º) qd :designvalueofverticalactionfromtopofslicesegment(kN/m) θ :angleofbottomofslicesegmenttohorizontal(º) Wd :designvalueoftotalweightofslicesegmentperunitoflength,totalweightofsoilandwater
(kN/m) PHd :designvalueofhorizontalactiononsoilmassofslicesegmentincircularslip(kN/m) a :lengthofarmfromcenterofcircularslipfailureatpositionofactionofPHd(m) R :radiusofcircularslipfailure(m)
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The design values in the equation can be calculated using the following equation by multiplying thecharacteristicvaluebythepartialfactor.Provided,however,thatWdshallbeexpressedbythesumofW’dandtheweightofwater,becauseitisnotnecessarytomultiplytheweightofwaterbyapartialfactor.Ifpartialfactorsarenotparticularlydesignated,1.00canbeusedforallpartialfactorsinequation (3.2.4).
cd =γc ck,W'd =γW' W'k,qd =γq qk,φd =tan–1(γtanφ' tanφk ),PHd =γPH PHk (3.2.4)
(6)ApplicabilityofStabilityAnalysisMethods6),7)SolutionsinstabilityanalysisbythemodifiedFelleniusmethodandthesimplifiedBishopmethodareinagreementforcohesivesoilinwhichφ=0,whenallpartialfactorare1.00,butdifferwhenthecirculararcpassesthroughsandyground.InJapan,circularslipfailureanalysisbythemodifiedFelleniusmethodiswidelyused.ThisisbecauseithasbeenreportedthatthemodifiedFelleniusmethodreasonablyexplainstheactualbehaviorsofslopefailurebasedontheresultsofanalysisofcasehistoriesofslipfailuresinportareasinJapan,4)andalsogivesasafetysidesolutionforsandyground. However,whenthefoundationgroundconsistsentirelyofsandysoillayers,orwhenaslipcirclecutsthroughground consisting of an upper thick sandy layer and lower cohesive soil layer, it is known that themodifiedFellenius method underestimates stability evaluated by the ratio expressed by the design value of shearingresistance/designvaluebasedonactions.7)Fromtheviewpointofthebasicprinciplesofthestabilitycalculationmethod,thesimplifiedBishopmethodismoreaccurateundersuchconditions.Therefore,thesimplifiedBishopmethodisgenerallyusedincaseofeccentricandinclinedloads,whichareparticularlyaproblemwhenexaminingthebearingcapacityofmounds(see2.2.5 Bearing Capacity for Eccentric and Inclined Actions).ItshouldbenotedthatthesimplifiedBishopmethodhastheproblemofoverestimatingtheratioexpressedby“designvalueofshearingresistance”/“designvalueofshearingforcesbasedonactions”whenactionsonnear-horizontalsandygroundapplyverticalloads.Insuchcases,amethodofstabilitycalculationcanbeusedwhichassumesthattheratiooftheverticaltothehorizontalforcesbetweenslicesis1/3.5oftheangleofsliceinclination.8)Instabilityverificationinthiscase,calculationsaremadeusingthefollowingequation.Inthisequation,thesymbolγisthepartialfactorforitssubscript,andthesubscriptskanddarethecharacteristicvalueanddesignvalue,respectively.
(3.2.5)
n
Basedonequation (3.2.5),γFfFfiscalculated,andstabilitycanbeverifiedbytheverificationparameterFf≥1.Thedesignvaluesinthisequationcanbecalculatedusingthefollowingequation.Provided,however,thatWdshallbeexpressedbythesumofW’dandtheweightofwater,becauseitisnotnecessarytomultiplytheweightofwaterbyapartialfactor.Ifpartialfactorsarenotparticularlydesignated,1.00canbeusedforallpartialfactorsinequation(3.2.6).
cd =γc ck,W'd=γW' W'k,qd=γq qk,φd=tan–1(γtanφ tanφk),PHd=γPH PHk (3.2.6)
wheren =1+tanθtan(βθ),β isaparameterwhichprovidestheratiooftheverticalforcetothehorizontalforceactingonthesidesoftheslice,andcanbeassumedtobeβ=1/3.5.Theothersymbolsarethesameasthoseinequation(3.2.3).
3.2.2 Stability Analysis Assuming Slip Surfaces other than Circular Slip Surface
(1)Despitetheprovisionsstatedintheprevioussections,alinearoracompoundedslipsurfaceshallbeassumedinstabilityanalysiswhenitismoreappropriatetoassumeaslipsurfaceotherthanacirculararcslipsurfacesaccordingtothegroundconditions.
(2)Whenlinearslipisassumed,examinationofstabilityagainstslipfailureofaslopewithastraightslidingsurfaceiscalculatedusingthefollowingequation.
(3.2.7)
where cd :designvalueofcohesionofsoil(kN/m2) φd :designvalueofangleofshearingresistanceofsoil(º) :lengthofbaseofslice(m) W'd :designvalueofeffectiveweightofsliceperunitoflength(kN/m)
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Wd :designvalueoftotalweightofsliceperunitoflength(kN/m) θ :inclinationofbaseofslice,assumedtobepositiveinthecaseshowninFig. 3.2.2(º) PHd :designvalueofhorizontalactionperunitoflengthappliedtoslicesegmentofslope,actions
includewaterpressure,actionsduetowavesandactionsduetogroundmotion(kN/m) γa :partialfactorforanalysismethod
ThepartialfactorγRfortheanalysismethodforslipfailurecanbe≧1.2inthepermanentsituationand≧1.00forvariablesituationsinrespectofLevel1earthquakegroundmotion. Thedesignvaluesinthisequationcanbecalculatedusingthefollowingequation.Provided,however,thatWdshallbeexpressedbythesumofW’dandtheweightofwater,becauseitisnotnecessarytomultiplytheweightofwaterbyapartialfactor.Ifpartialfactorsarenotparticularlydesignated,1.00canbeusedforallpartialfactorsinequation (3.2.8).
cd =γc ck,W'd =γW' W'k,φd =tan–1(γtanφ tanφk), PHd =γPH PHk (3.2.8)
Fig. 3.2.2 Examination of Slope Stability Analysis using Linear Sliding Surface
References
1) R.F,Scott:PrincipleofSoilmechanics,AddisonWesley,p.431,19722) Tsuchida,T.andTANGYiXin:TheOptimumSafetyFactor forStabilityAnalysesofHarbourStructuresbyUseof the
CircularArcSlipMethod,Rept.ofPHRIVol.5、No.1、pp.117-146,19963) Yamaguchi,K.:SoilMechanics(FullyRevisedEdition)Chapter7,Stabilityanalysisofearthstructure,Giho-doPublishing,
pp.197-223,19694) Nakase,A.:Theφ=0analysisofstabilityandunconfinedcompressionstrength,SiolandFoundation,Vol.7,No.2,pp.33-50,
19675) A.W.Bishop:Theuseoftheslipcircleinthestabilityanalysisofslopes,Geotechnique,Vol.5,No.1,pp.7-17.19556) Nomura,K.,T.Hayafuji andF.Nagatomo:ComparisonbetweenBishop’smethod andTschebotarioff’smethod in slope
stabilityanalysis,Rept.ofPHRIVol.7No.4,pp.133-175,19687) Kobayashi,M.:Outstandingissuesinstabilityanalysisofground,ProceedingsofAnnualConferenceofPHRI1976,pp.73-
93,19768) Tsuchida,T.,M.KobayashiandT.Fukuhara:Calculationmethodforbearingcapacitybycircularslipanalysisutilizingslice
method,Proceedingsof33rdConferenceonGeotechnicalEngineering,pp.1371-1372,1998
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
4 Soil Improvement Methods4.1 General
Whencarryingoutsoilimprovementasacountermeasureagainstpossiblefailuresofsoftground,anappropriatemethodshallbeselectedinviewofthecharacteristicsoffoundationsubsoil,typeandscaleofstructure,easeandperiodofconstruction,economicfactorsandinfluenceontheenvironment.
4.2 Liquefaction Countermeasure Works
Incarryingoutliquefactioncountermeasureworks,itispreferabletoconductanappropriateexaminationofthefollowingitemsinordertomaintainthefunctionsofthefacilities.
①Methodofcountermeasureworks② Scopeofexecutionofcountermeasureworks(executionareaanddepth)③ Concreteperformanceverificationofcountermeasureworks
4.3 Replacement Methods
(1) Intheperformanceverificationofthereplacementmethod,itisnecessarytoconsiderstabilityagainstcircularslipfailure,settlementofsubsoil,andconstructabilityofreplacement.
(2)Replacement methods can be divided into two methods including the replacement of subsoil by excavation(foundationreplacementbyexcavation)andtheforcedreplacement.Inthereplacementofsubsoilbyexcavationmethod,softsoilisexcavatedandremovedbyasuctiondredgeroragrabdredgerandreplacedbyfillingwithgoodqualitysoil. Thismethod iswidelyused inoffshoreworks. On theotherhand, theforcedreplacementmethodisamethodinwhichsoftsoilisforciblypushedoutbyembankmentload,sandcompactionpiles,blasting,orothermethods,andisthenreplacedwithgoodqualitysoil.39)
(3)The following presents the performance verification method for the replacement of subsoil by excavation(foundationreplacementbyexcavation),whichiswidelyusedinoffshoreworks.
① ProcedureofperformanceverificationIntheperformanceverificationofthereplacementmethods,asshowninFig. 4.3.1,itisgenerallypreferabletocarryouttheperformanceverificationbyaprocedureofassumptionoftheverificationconditions,assumptionof the verification cross section including replacement depth, replacement width, and slope of excavation,examinationofcircularslipfailure,examinationofsettlement,andselectionofthereplacedsand.AlthoughnotshowninFig. 4.3.1,itisalsonecessarytoexaminethepossibilityofliquefactionofthereplacedsandandtheevaluationoftheeffectthereof.
Examination of circular slip failure
Examination of settlement
Permanent state
Setting of design conditions
Assumption of cross-sectional dimensions
Evaluation of actions
Selection of replaced sand
Performance verification Performance verification
Fig. 4.3.1 Example of Performance Verification Procedure for Replacement Method
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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② ExaminationofslipfailureIn theexaminationof slip failurebycircular slip failure calculations,3 Stability of Slopes canbeusedasa reference. For partial factors, related provisions inPart III of thisTechnical Standard can be used as areference,asnecessary. Incalculatingtheearthpressureonsheetpilesoranchorageworksinsidethereplacedsection,itispreferabletoconductanexaminationof thecompositeslipinadditiontotheconventionalearthpressurecalculations.Incaseswheretheentirelayeristobereplacedandthebaserockstratumisinclined,itispreferabletoconductanexaminationforacompositeslipwhichincludesslipfailureonthebaserock.
③ ExaminationofsettlementWhencohesivesoilremainsbeneaththereplacedcrosssection,suchasbeneathpartialreplacementortheslopeoffoundationexcavation,consolidationsettlementcanbeexpectedinthecohesivesoilportion.Therefore,itispreferabletoconductanexaminationoftheeffectofthisconsolidationsettlementonthesuperstructure.
④ SelectionofreplacedsandItispreferablethatthereplacedsandhasagoodgrainsizedistributionandhasalowcontentofsiltcontent.Ingeneral,theratiooffinescontentisfrequentlyspecifiedasnomorethan15%.Theangleofshearresistanceofreplacedsandcangenerallybeassumedtobearound30º.However,thisvalueisaffectedbytheparticlesize,sizedistribution,placementmethod,sequenceofplacement,elapsedtime,surcharge,andotherfactors.Thereisacasewheretheangleofshearresistanceisextremelylow,andthereforecautionisnecessary.
⑤ ExaminationofLiquefactionLiquefactionisgenerallyassessedbasedonthegrainsizedistributionandtheN-valuesofthereplacedsand.Whendifficulttoevaluate,theliquefactionshouldbeexaminedbycyclictriaxialtest41)(seePart II, Chapter 6 Ground Liquefaction).Whenliquefactionisoneofcriticalfactorsinthedeterminationofthereplacementsectionandthecharacteristicsofthereplacementsand,itshouldbeconsideredatselectingthereplacedmaterial.Ifinsufficientstrengthofthereplacedsandisexpected,itispreferabletocompactthereplacedsandafterfilling.
⑥ TheN-valuesofthereplacedsandareaffectedbyitsgrainsizeandgrainsizedistribution,placementmethodand sequence of placement, elapsed time and surcharge. According to some case studies, theN-values ofthereplacedsandwerearound10whensandwasinstantaneouslyplacedinlargevolumefromlarge-capacityhopperbargeswithbottomdoors,around5whensandwasplacedbygrabbucketsfromsandcarriers,andevensmallervalueswhensandwasspreadbysuctiondredger.SeveralcasestudiesshowthattheN-valuesoftheloosereplacedsandincreasedwiththeapplicationofsurchargeandtheelapsedtimeafterplacingthereplacedsandorrubblestonesorplacingcaisson.
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4.4 Vertical Drain Method4.4.1 Fundamentals of Performance Verification
(1) Intheverticaldrainmethod,itisnecessarytosecurethefollowingperformancecorrespondingtothepurposesofimprovement.
① Assuretargetedstrengthincrease.② Assurethatresidualsettlementshouldbewithintheallowablevalue.③ Securethenecessarystabilityofthefacilities.
(2)AnexampleoftheperformanceverificationprocedurefortheverticaldrainmethodisshowninFig. 4.4.1.
Constructionperiod
Determination of type,diameter, and spacing of drains
Allowablesettlement
Bearingcapacity
of groundAssumption of target strength increase
Verification of stabilityagainst circular slip failure
Determination of embankmentwidth and shape
in each stage of construction
Assumption of necessaryconsolidation load
Assumption of sectionto be improved
Assumption of height, weight,and shape of embankment
Determination of embankmentheight and consolidation period in
each stage of construction
Verification of stability againstcircular slip failure
Comparison of economy
Fig. 4.4.1 Example of Performance Verification Procedure for Vertical Drain Method
4.4.2 Performance Verification
(1)DeterminationofHeightandWidthofEmbankment
① Heightandwidthofembankmentnecessaryinsoilimprovement
(a) Theheightandwidthoftheembankmentwhenanembankmentistobeusedasconsolidationloadbythepreloadmethodor surchargemethod shall bedeterminedconsidering the strength increasenecessary forstability of the embankment during and after construction, the stability and allowable settlement of thefacilitiestobeconstructed,theeffectonthesurroundingarea,andotherrelevantfactors.
(b)Itispreferabletosetthetopwidthoftheembankmentlargerthanthewidthrequiredforsoilimprovement(seeFig. 4.4.2).
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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H
h
Mean widthMean width
Fill top width (Fill)
Fill top width (Fill)
Drain areaDrain area
(Permeable layer)(Permeable layer)
Fig. 4.4.2 Width of Embankment for Vertical Drain Method
(c) Inexaminationofthestrengthincrease(Δc)oftheoriginalground,equation (4.4.1)canbeused.
(4.4.1)where
Ca :targetstrengthincrease(kN/m2) h :heightofembankment(m) p0′ :initialpressure(verticalpressurebeforestartofconstruction)(kN/m2) pc′ :preconsolidationpressure(kN/m2) U :degreeofconsolidation α :coefficientofstressdistribution,namelyratioofdistributedstressingroundandconsolidation
load(embankmentload) γ′ :effectiveunitweightofembankment(kN/m3) Δc :strengthincrease(kN/m2)Δc/Δp:increaserateofstrength
② Evaluationofstabilityofembankment
(a) It isnecessarytoverifythestabilityofembankmentsbycircularslipfailureanalysisorotherappropriatemethodsfortheheightandwidthoftheembankmentdeterminedbytheaboveexplanationof① Height and width of the embankment necessary in soil improvement.Incaseswhereitisnotpossibletosecurethestabilityof theembankment itself, it isnecessary todivide thefinal embankment into several stagesandperformverificationofthestabilityineachoftheembankmentstages.
(b)EvaluationofstabilityofembankmentagainstslipfailureIn the examination of the stability of an embankment by circular slip failure calculations,3 Stability of Slopescanbeusedasareference.Forthepartialfactorstobeusedinthecalculations,thepartialsafetyfactorsforthecircularslipfailurecalculationsinconnectionwithrespectivefacilitiescanbeused.Inthiscase,thestrengthofthegroundmustconsiderthestrengthincreasecalculatedbyequation(4.4.1).
(c) RoughestimationofstrengthincreaseSincesurchargeisusuallyappliedinseveralstagesintheverticaldrainmethod,thedegreeofconsolidationU tobeusedinequations(4.4.1)and(4.4.2)differsateachsurchargestage.However,strengthincrementmayoftenbecalculatedbyassumingauniformdegreeofconsolidationofapproximately80%.
(2)PerformanceVerificationofDrainsIntheperformanceverificationofdrains,itisnecessarytomakecalculationswhichconsiderthepermeabilitycharacteristicsofthedrainmaterial,andpermeabilitycharacteristicsandthicknessofthesandmat,inadditiontothedraininterval,draindiameter,anddrainageconditionsatthetopandbottomofthelayertobeconsolidated.
① Drainsandsandmats
(a) Drainsandsandmatsshallpossesstherequireddrainagefunctions.
(b)ConsolidationrateanddraindiameterTheconsolidationrateisapproximatelyproportionaltothedraindiameterandinverselyproportionaltothesquareofthedraininterval.Generally,theamountofdrainmaterialcanbereducedbyplacingsmalldiameter
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drainsatsmallintervalsratherthanbyplacinglargediameterdrainsatwideintervals.However,inthesanddrainmethod,useofsandpileswithanexcessivelysmalldiametermayresultincloggingduetoinfiltrationofclayeyparticles,andthereisadangerofbreakageofthesandpilesifthepilesareunabletofollowdeformationbyloadingorconsolidationsettlementduringtheconsolidationperiod.Constructionrecordsofsanddrainmethodtodateshowthat themostfrequentlyuseddiameter is40cm,anddiametersnormallyrangefrom30-50cm.Inthesmalldiameterfabri-packeddrainmethod,43)sandpileswithadiameterof12cmarepackedintosyntheticfiberbags,andfoursandpilesareinstalledsimultaneouslyusingalightweightpiledriver.Thismethodisfrequentlyusedwithextremelysoftsubsoilonland.Afabri-packeddrainmethodwithadiameteroftheorderof40cmhasalsobeendevelopedforimprovementofextremelysoftsubsoilattheseabottom.44),45)
(c)MaterialsforsandpilesSandusedforsandpilesshouldhavehighpermeabilityaswellasasuitablegrainsizetopreventcloggingwithclayeyparticles.ThegrainsizedistributionsofsandusedinworksareshowninFig. 4.4.3.However,casesinwhichsandwithasomewhathigherfinescontentisusedhavealsoincreasedinrecentyears.
Grain size(mm)
1
2
3 4
56
7
B
9
1011
12
A
0
20
40
60
80
100
0.1 1 10
Silt Fine sand Coarse sand Gravel
Examples in Japan121
8New YorkA B
Pass
ing
wei
ght p
erce
ntag
e (%
)
Fig. 4.4.3 Examples of Sand Used in Sand Piles
(d)PrefabricateddrainsandrelatedmaterialsIntheperformanceverificationoftheprefabricationdraintypeofstrip-shapeddrain,thewidthandthicknessofapproximately10cmand5cmrespectively,theobjectdrainisconvertedtoacirculardrainhavingthesamecircumferentiallength.Inpracticalcases,however,theperformanceverificationisconductedasequivalenttoasanddrainhavingadiameterof5cm.42)Cautionisnecessaryincaseswherethedrainagecapacityofthedrainislow,asthereisatimelaginconsolidationattheendoftheverticaldrain(i.e.,lowerpartoftheconsolidationlayer).
(e) SandmatsThethicknessofthesandmatlayerisusuallysettobeapproximately1.0mto1.5mformarineworksand0.5mto1.0mforlandworks.Athicksandmatlayermaycausedifficultyindrainpiledriving.Ontheotherhand,athinsandmatlayermayshowreducedpermeabilityduetoinfiltrationofclayeyparticles. Wherethethicknessofthesandmatlayerisconcerned,whenthedrainagecapacityofthesandmatlayerislow,adelayinconsolidationmayoccurduetoheadloss.Inthiscase,itispreferabletoimprovepermeabilitybyinstallingdrainagepipesinthesandmatlayer.Inrecentyears,amethodwhichdoesnotrequireasandmathasbeendevelopedbyconnectingtheexcesslengthsofdrainsinagrid-likeshapetosecuredrainagepathsinthehorizontaldirection.50)
② Draininterval
(a) Intervalofdrainpilesshallbesodeterminedthattherequireddegreeofconsolidationcanbeobtainedinagivenconstructionperiod.
(b)GeneralTheverticaldrainmethodcanbeappliedwhentherateofconsolidationbythepreloadingmethod,surchargemethod,vacuumconsolidationmethod,orsimilarmethodsisslowconsideringthetimeconstraintsof theconstructionperiod.Fig. 4.4.4 showstherelationshipbetweentherequiredconsolidationtimet80,drainage
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distanceH,andcoefficientofconsolidationcvofaclayeylayerbythepreloadingmethod,surchargemethod,andvacuumconsolidationmethod. Note)InFig. 4.4.4,theunitsusedareconsolidationtimet80(day),drainagedistanceH(m),andcoefficientofconsolidationcv(cm2/min).
1 5 10 50H(m)
U10%20%30%40%50%
60%
70%80%90%
T/T800.0130.0550.1250.222
0.348
0.507
0.7111.0001.497
6months
1year
3years
2years
4years5years
10
50
100
500
1000
5000
10000
Permeable layerPermeable layer
Permeable layerPermeable layer
Permeable layerPermeable layer
Impermeable layerImpermeable layer
Clay
Clay
0.2
2H
H
(d)
10years
t 80
c ν=0
.01c
m /m
in2
c ν=0
.01c
m /m
in2
0.3 0.4
0.60.8
1.0
0.10.08
0.06
0.04
0.03
0.02
Fig. 4.4.4 Required Days for 80% Consolidation of Clay Layer
(c) DeterminationofdrainInterval ThedrainintervalcanbeobtainedfromFig. 4.4.5 andequation (4.4.3)basedontheBarrontheoryorBiotheory.51)Ithasbeenpointedoutthatconsolidationmaybedelayedduetotheeffectofthesmear,whichmeansthedisturbanceofcohesivesoilgroundbydraindriving,ifthedrainintervalisexcessivelysmall52),53),54),55).
(4.4.3)where
D :draininterval(cm) β :factorrelatedtoarrangementofdrains
withsquarearrangement,β=0.886,andwithatriangulararrangement,β=0.952.
n : (n canbeobtainedfromFig. 4.4.5)
De :effectivediameterofdrain(cm) Dw :diameterofdrain(cm)
Th’ :parametersimilartotimefactor
cvh :coefficientofconsolidationrelatedtoflowofwaterinhorizontaldirection(cm2/min) t :consolidationtime(min)
Note)Theunitusedfortime(t) inFig. 4.4.5 andFig. 4.4.6 isdays.
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Fig. 4.4.5 Calculation Chart for N-value
(d)FlowofwaterinverticaldirectionIntheverticaldrainmethod,consolidationbyflowofwaterinthehorizontaldirectionisexpected.However,whenthe thicknessof the layer tobeconsolidated iscomparativelysmall incomparisonwith the intervalbetweenthedrains,progressofconsolidationduetoflowofwaterintheverticaldirectioncannotbeignored.Fortheperformanceverificationofthepileintervalconsideringconsolidationduetoverticalflowofwater,Reference49)canbeusedasareference.
(e) CoefficientofconsolidationinhorizontaldirectionNoappropriatetestmethodhasbeenestablishedforthecoefficientofconsolidation(cvh)forflowofwaterinthehorizontaldirectionofcohesivesoillayers.Ingeneral,thecoefficientofconsolidationinthehorizontaldirectionisconsideredtobe5-10timesgreaterthanthatintheverticaldirection,butsomereportssaythattheyare equivalent. If the effectsofhead loss in thedrains and theeffectof smear are considered, it isnotnecessarilyadvisabletousetheresultsofconsolidationtestswhichreproducetheflowofwaterinthehorizontal direction. According to examples of construction to date, there are no practical objections tosubstitutionofthecoefficientofconsolidation(cv)forflowofwaterinthehorizontaldirectionofclayeysoillayers.
(f) CalculationofdegreeofconsolidationAfterdeterminingthedraininterval,therelationshipbetweenthedegreeofconsolidationandelapsedtimecanbeobtainedusingequations (4.4.4)and(4.4.5)andFig. 4.4.6.
(4.4.4)
(4.4.5)
where Th :timefactorofconsolidationforflowofwaterinhorizontaldirection cvh :coefficientofconsolidationforflowofwaterinhorizontaldirection(cm2/min) t :elapsedtimefromstartofconsolidation(min) De :effectivediameterofdrainarea(cm) Dw :diameterofdrain(cm)
Note)InFig. 4.4.6,theunitsusedarecoefficientofconsolidationcvh(cm2/min),effectivediameterofdrainareaDe(cm),andelapsedtimet (day).
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Fig. 4.4.6 Calculation Chart for Degree of Consolidation
(g)EffectivediameterofdrainareaTheeffectivediameterofdrainareaDe isthediameterofanequivalentcirclethathasthesameareaasthesoilbeingdrainedbyasandpile.TherelationshipbetweenDe andintervalofthedrainpileD isasfollows:
De =1.128D forsquaregridpattern. (4.4.6)De =1.050D forequilateraltriangulargridpattern. (4.4.7)
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4.5 Deep Mixing Method4.5.1 Fundamentals of Performance Verification
[1] Scope of Application
(1)Thedeepmixingmethoddealtwithinthissectionistheoneinwhichthesoilin-situismixedmechanicallywithcement.
(2)Themajorityofexamplesofapplicationofsoilimprovementbythedeepmixingmethodinportsarebreakwaters,revetments including partition dikes, and quaywalls having caissons or the like as their superstructure. Theperformanceverificationmethodpresentedherecanbeappliedtoimprovedsoilwhenagravity-typebreakwaterrevetmentorquaywallistobeusedasthesuperstructure.
(3)When applying the deepmixingmethod to port facilities, a high rigidity subsurface structure is formed bymutuallyoverlappingstabilizedsoilhavingapileshapeinthegroundusingamixingmachine.Thepatternofthissubsurfacestructureisdetermineddependingonthepropertiesofthegroundandthetypeandscaleofthesuperstructure.Ingeneral,however,theblocktypeandthewalltypeshowninFig. 4.5.1arefrequentlyused.Accordingly,blocktypeimprovementandwalltypeimprovementwillbediscussedherewhicharerepresentativeformsofimprovementinthefieldofportengineering.
(4)ThewalltypeimprovementconsistsoflongandshortwallsasshowninFig. 4.5.1(b).Thebasicconceptofthedesignisthatthelongwallsfunctiontotransmittheexternalactionstothefoundationground,whiletheshortwallsfunctiontoincreasetheintegrityoftheimprovedground.
Long wallShort wall
Soft subsoil Improved subsoilImproved subsoil
Seabed
Sea surfaceSea surface
Sea surface
Soft subsoilSoft subsoilSoft subsoilSoft subsoil
Sea surface
Sea surfaceSea surface
Seabed
Soft subsoil Improved subsoilImproved subsoil
(a)blocktypeimprovement (b)walltypeimprovement
Fig. 4.5.1 Typical Improvement Patterns in the Deep Mixing Method
[2] Basic Concept
(1)Definitionsofthetermsareasfollows;
① Stabilizedsoil:Improvedsoilproducedbythedeepmixingmethod.
② Stabilizedbody:Akindofstructureformedundergroundwithstabilizedsoil.
③ Improved ground: Portion in which the stabilized body and untreated soil is combined. In the wall typeimprovement,theuntreatedsoilbetweenthelongwallsisinclusive.
④ Improvedsubsoilsystem:Portionabovethebottomoftheimprovedsubsoil,betweentheverticalplanespassingthroughthefronttoeandheeloftheimprovedsubsoil.
⑤ Externalstability:Examinationofstabilityofunifiedbodyconsistingofimprovedsubsoilandsuperstructureasarigidbodyintheprocessuptofailure.
⑥ Internalstability:Examinationofinternalfailureofthestabilizedbodywhichisstableexternally.
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⑦ Bottomseatedtype:Structuraltypeinwhichthestabilizedbodyisseateddirectlyonthebearingstratum;inthistypeofimprovement,actionsaretransmittedtothebearingstratumbyimprovementofthesoftgroundreachingasfarasthebearingstratum.
⑧ Floatingtype:Structuraltypeinwhichthestabilizedbodytakesaformthatfloatsinthesoftground;inthistypeofimprovement,thestabilizedbodyisnotseatedonthebearingstratum,butsoftgroundisallowedtoremainunderneaththestabilizedbody.
(2)Stabilizedsoilbythedeepmixingmethodgenerallyhasextremelyhighstrengthanddeformationmodulusandextremelysmallstrainatfailureincomparisonwiththesoiloftheoriginalground.60)Accordingly,astabilizedbody formedwith stabilized soil can be regarded as a kind of structure. Therefore, examination of externalstabilityofthestructureasawhole,examinationoftheresistanceofthestructureitself,andwhenparticularlynecessary,examinationofthesettlement,horizontaldisplacement,androtationofthestabilizedbodyasarigidbodyshallbeperformed.
(3)Intheperformanceverificationofthedeepmixingmethod,theTechnical Manual for the Deep Mixing Method in Marine Construction Works 61)canbeusedasareference.
(4)An example of the procedure of the performance verification for the deep mixing method for gravity-typestructuresisshowninFig. 4.5.2.
Permanent state
Variable states in respect of Level 1 earthquake ground motion
Permanent state
Accidental states in respect ofLevel 2 earthquake ground motion
Determination of design conditions
Assumption of dimensions of stabilized body
Evaluation of actions including setting of seismic coefficient for verification
Determination of dimensions of stabilized body
Performance verificationPerformance verification
*2
*1
Verification of external stability such as sliding, overturning and bearing capacity
Verification of external stability such as sliding, overturning and bearing capacity
Verification of internal stability such as toe pressure, shear stress and dislodging
Verification of internal stability such as toe pressure, shear stress and dislodging
Examination of deformation by dynamic analysis
Examination of deformation by dynamic analysis
Examination of circular slip failure and settlement
*1:Whennecessary,examinationofdeformationbydynamicanalysiscanbeperformedforLevel1earthquakegroundmotion.Incaseswhere thewidthoftheimprovedsubsoilissmallerthanthewidthofthefoundationmound,itispreferabletoconductanexaminationof deformationbydynamicanalysis.*2Dependingontheperformancerequirementsofthemainbody,examinationforLevel2earthquakegroundmotionshallbeperformed.
Fig. 4.5.2 Example of Procedure of Performance Verification of Deep Mixing Method
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(5)TheperformanceverificationofvariablesituationsinrespectofLevel1earthquakegroundmotioninthedeepmixingmethodcanbeconducted,equivalenttogravity-typequaywalls,byeitherthesimplifiedmethod(seismiccoefficientmethod),orbyadetailedmethod(nonlinearseismicresponseanalysisconsideringdynamicinteractionofthegroundandstructures)presentedinPart III, Chapter 5, 2.2.3 Performance Verification.Incaseswherethewidthoftheimprovedsubsoilissmallerthanthewidthofthefoundationmoundintheresultsofverificationbythesimplifiedmethod,itisnecessarytocarryoutanexaminationofdeformationoftheimprovedsubsoilandmainbodybyadetailedmethod.ExaminationofaccidentalsituationsinrespectofLevel2earthquakegroundmotionmayalsobenecessarydependingontheperformancerequirementsofthefacilities.
(6)Intheperformanceverificationofthedeepmixingmethod,itisnecessarytoconsiderthefollowingitems.
① Becausethereisnomethodforthedeepmixingmethodtodeterminethedimensionsofthestabilizedbodyatonce,theverificationcalculationisperformedrepeatedlyuntilstabilityconditionsaresatisfiedandthemosteconomicalcrosssectionisobtained.
② Inimprovedsubsoilbywall-typeimprovement,itisnecessarytodeterminethedimensionsofboththelongwallsand theshortwalls. Because the longwallsandshortwallsareconstructedbymutuallyoverlappingpilebodiesofstabilizedsoil,thecross-sectionalshapesofthewallscannotbedeterminedarbitrarilyanditisnecessarytoconsiderthedimensionsofthemixingmachinewhichisexpectedtobeused.
③ Inimprovedsubsoilbywall-typeimprovement,untreatedsoilbetweenthelongwallsexistsintheimprovedsubsoil;therefore,intheexaminationoftheinternalstability,itisnecessarytoexaminetheextrusionoftheuntreatedsoilbetweenthelongwalls,inadditiontotheexaminationoftheinternalstressinthestabilizedbody.
④ Thelimitvaluesofdeformationinthevariablesituationsandtheaccidentalsituationscanbesetcorrespondingtotheperformancerequirementsofthefacilities,usingdeformationofthemainstructuretobesupportedbythedeepmixingmethodasanindex.
⑤ IntheverificationofdeformationofLevel1earthquakegroundmotionandLevel2earthquakegroundmotion,it ispreferable touseanumericalmodelorresultsofshakingtable testswhichcanappropriatelyassess theresidualdeformationoftheimprovedsubsoilcausedbygroundmotion.
4.5.2 Assumption of Dimensions of Stabilized Body
[1] Mixing Design Method for Stabilized Subsoil
Itisnecessarytodeterminethemixingdesignofthestabilizedsubsoilbyperforminglaboratorymixingtestsorin-situtestsunderthesameconditionsasinactualconstruction.
[2] Material Strength of Stabilized Body
(1)Allowablestressofthestabilizedbodyneedstobeappropriatelydeterminedfortheexaminationoftheinternalstability.
(2)Design compressive strength fc can be obtained using equation (4.5.1) based on the standard design strengthquc. Inthisequation, thesymbolγ is thepartialfactorfor itssubscript,andthesubscriptskandddenotethecharacteristicvalueanddesignvalue,respectively.
(4.5.1)where
fc :designcompressivestrengthofstabilizedbody(kN/m2) α :factorforeffectivecross-sectionalarea β :reliabilityindexofoverlap quc :designstandardstrength(kN/m2)
Thedesignvaluesintheequationcanbecalculatedusingthefollowingequation.
qucd=γ quc quck
Forthepartialfactorγqucofdesignstandardstrength,thevaluesmentionedin4.5.4 Performance Verification, [2] Examination of Internal Stability maybeused.
(3)Thedesignshearstrengthfshanddesigntensilestrengthft ofthestabilizedbodycanbeobtainedfromequation (4.5.2) andequation(4.5.3)usingthedesigncompressivestrengthfc.
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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(4.5.2)
(4.5.3)where
fsh :designshearstrengthofstabilizedbody(kN/m2) ft :designtensilestrengthofstabilizedbody(kN/m2)
(4)In the performance verification of the stabilized body, the stabilized body is assumed to be amaterial withhomogeneousstrength.However,inactualconstructionwork,becausethestabilizedbodyisformedbymutualoverlappingofpilesofstabilizedsubsoil,therearecasesinwhichinhomogeneousbystabilizedsoilremains,forexample,containingresidualuntreatedsoilorhavingstrengthdifferencesinoverlappedparts,dependingonthemixingmachineusedandthemethodofoverlapping.Thefactorsαandβshowninequation(4.5.1)arefactorsfortreatingstabilizedsubsoilasmaterialhavinghomogeneousstrength.Theconceptswhensettingthesefactorsarepresentedinthefollowing.
① Factorforeffectivecross-sectionalareaαWhenconstructioniscarriedoutusingmachineswithmultiplemixingblades,thecrosssectionofthestabilizedbodyconsistsofmultiplecylindersasshowninFig. 4.5.4.Inblock-typeandwall-typeimprovement,the stabilizedbody is formedbyoverlapping stabilized subsoil havingapile shapeas shown inFig. 4.5.5.Therefore,unimprovedportionsremainaroundtheoverlappingparts,andtheareaoccupiedbythestabilizedsubsoilissmallerthaninotherareas.Thefactorforeffectivecross-sectionalareaαisafactorforcorrectingthisunimprovedpart. Thevalueofthefactorforeffectivecross-sectionalareawilldifferdependingonthedirectionandtypeoftheactionssuchascompressive,tensileandshearwhicharetheobjectoftheperformanceverification.Forexample,whenconsideringshearforceintheverticaldirectionofthestabilizedbodyorstressactingperpendiculartooverlappingparts,examinationonthenarrowestconnectingsectiongivessafesideresults.Ontheotherhand,whenconsideringnormalstressintheverticalplaneofthestabilizedbody,theentireareaofthestabilizedbodymaybeconsideredasactingeffectively.Here,thefactoraccordingtotheformerconceptisusedasthefactorforeffectivecross-sectionalareafortheeffectivewidthα1,andthefactoraccordingtothelatterconceptisusedasthefactorforeffectivecross-sectionalareafortheeffectiveareaα2.
Dx
x
Dy
y
D
R
L
d
Connecting surface
Width ofoverlapping
Fig. 4.5.3 Effective Width inherent in Deep Mixing Machine Fig.4.5.4 Connecting Surfaces
(a) Factorforeffectivecross-sectionalareaforeffectivewidthα1Thefactorforeffectivecross-sectionalareaforeffectivewidthα1shallgenerallybethesmallerofthevaluesobtainedusingequation(4.5.4)andequation(4.5.5).
1) FactorformixingmachinesInFig. 4.5.3,assumingtheintervalbetweenthemixingshaftsofthemixingmachinesisDxandDyandtheoverlappedlengthoftheimprovedpilesislxandly,thecoefficientα1determinedbythemixingmachinescanbeobtainedusingequation (4.5.4).
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(4.5.4)
2) FactorforoverlapInFig. 4.5.4,assumingtheintervalbetweenthemixingshaftsisD,theradiusofthemixingbladeisR,andtheoverlapwidthisd,thefactorα1foroverlapcanbeobtainedusingequation(4.5.5).
(4.5.5)
Inmanyexamples,theminimumoverlapwidthdisassumedtobe25cm,consideringexecutionaccuracyandcapacity.
(b)Factorforeffectivecross-sectionalareaforeffectiveareaα2Thefactorfortheeffectiveareaα2canbeobtainedusingequation(4.5.6).
(4.5.6)where
A1 :areaenclosedbyboldlineinFig. 4.5.4 A2 :areashownbyhatchedlinesinFig. 4.5.4
② ReliabilityindexofoverlapβAtoverlappedparts,anewimprovedpileisjoinedtotheexistingimprovedpileofstabilizedsubsoilwhichhasalreadybeguntoharden.Therefore,thereisapossibilitythatthestrengthofthispartmaybesmallerthanthatofotherparts.Thereliabilityindexofoverlapβisdefinedastheratioofthestrengthofoverlappedparttothatofotherimprovedpiles.Itsvaluewilldifferdependingontheelapsedtimeuntilthenewpileisjoinedtotheexistingpile,themixingcapacityofthemachine,thestabilizerfeedmethod.However,ingeneral,βmaybesettoapproximatelyβ=0.8–0.9.
(5)Relationshipbetweenstandarddesignstrengthandin-situandlaboratorymixingstrength Therelationshipbetweentheaveragevaluequf oftheunconfinedcompressivestrengthqufofin-situstabilizedsubsoilandthecharacteristicvaluequckofthestandarddesignstrengthisgivenbyequation (4.5.7).
(4.5.7)where
K :coefficientshowingnormaldeviation,namelymultiplierforstandarddeviationσ.Ingeneral, K =1.0canbeadopted. V :coefficientofvariationofunconfinedcompressivestrengthqufofin-situstabilizedsoil.
BecausethevalueofVisgreatlyaffectedbythemixingmachineandmixingtechnology,itispreferablethatVbesetindividuallyforeachcase.However,basedonthepastexamples,V =33(%)canbeused.
SettingofthevalueofthecoefficientKas1.0whenthevariationoftheunconfinedcompressivestrengthqufofin-situstabilizedsubsoilfollowsanormaldistributionmeansthatthecharacteristicvaluequckofthestandarddesignstrengthissetatastrengthwherethedefectoccurrenceratiois15.9%(seeFig. 4.5.5). Therelationshipbetweentheaveragevaluequf oftheunconfinedcompressivestrengthqufofin-situstabilizedsubsoilandtheaveragevaluequl oftheunconfinedcompressivestrengthqulofsamplesmixedinthelaboratoryisgivenbyequation (4.5.8).
(4.5.8)
Thevalueofλisaffectedbynumerousfactors,includingthemixingmachineandconstructionconditions,typeofsoilwhichistheobjectofimprovement,typeofstabilizer,thecuringenvironment,andage.Asaguideline,inoffshoreworks,λ=1canbeassumedwhenconstructionisperformedbylarge-ormedium-scaleworkingcrafts,andλ=0.5–1canbeassumedforsmall-scaleworkingcrafts.Provided,however,thatthevalueofλmayalsobedeterminedbasedontestsorthepastrecordsofconstruction. Aschematicdiagramoftherelationshipbetweendesignstandardstrengthquckandtheaveragevaluequl oftheunconfinedcompressivestrengthofsamplesmixedinthelaboratoryandtheaveragevaluequf oftheunconfinedcompressivestrengthofin-situstabilizedsoilisshowninFig. 4.5.5.
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0.0 0.5 1.0 1.5 2.0 2.5 3.0
quck qut = λ quck
15.9%15.9%
kσ=σ
Fig. 4.5.5 Relationship between quck, , and quck (schematic diagram)
4.5.3 Conditions of Actions on Stabilized Body 68)
(1)Fig. 4.5.6 shows a schematic diagram of the loads acting on the stabilized body in the case of gravity-typerevetmentsandquaywalls.
(2)Becauseimprovedsubsoilofwall-typeimprovementcontainsuntreatedsoilintheimprovedsubsoil,dependingontheperformanceverificationitems,itmaybenecessarytosettheloadconditionsbyseparatingtheuntreatedandstabilizedsubsoils.
(3)Fortheexaminationontheexternalstabilityofimprovedsubsoilsystems,PaorPpcanbedeterminedusingtheactiveandpassiveearthpressuresspecifiedinPart II, Chapter 5, 1 Earth Pressure.Whenexamininginternalstability,Pamaybeconsideredasactiveearthpressure. However, it ispreferable thatPpbesetappropriatelywithintherangefromearthpressureatrest topassiveearthpressure,consideringtheexternalstabilityof theimprovedsubsoilsystem.
(4)In caseswhere a certain amount of displacement of the improved subsoil is expected, it has been confirmedexperimentallythatadhesionofuntreatedsoilactsontheverticalplanesoftheactiveandpassivesidesofthestabilizedbody.Inthecaseofembankmentandreclamationbehindtheimprovedsubsoil,downwardnegativeskinfrictionaccompaniedbyconsolidationsettlementoftheuntreatedsoilactsontheverticalplaneoftheactivesideofthestabilizedbody.Therefore,thesetypesofadhesionshouldbeconsideredintheexaminationofthePermanentsituation.69)Ontheotherhand,intheexaminationofactionsassociatedwithgroundmotion,safetysideassumptions,forexample,thattheinertiaforceofthestabilizedbodyandtheearthpressureduringgroundmotionwillactsimultaneously,areadopted.Therefore,CuaasadownwardactionandCupasanupwardactionmaybeassumedintheexaminationofbothexternalandinternalstability.ThevalueofCuaandCupinthiscaseareobtainedfromtheundrainedshearstrengthoftheuntreatedsoilundertheseconditions.
(5)Inthecaseofimprovedsubsoilbywall-typeimprovement,itmaybeassumedthatbothPaandPpactuniformlyonthe longwalls and the untreated soil between the longwalls. Provided, however, thatwhen the subgradereactionTatthebottomofthestabilizedbodyisobtained,itisassumedthattheloadsactingonthestabilizedbody,suchastheweightofthemainbody,areconcentratedonthelongwalls,andonlytheself-weightoftheuntreatedsoilactsontheuntreatedsoilbetweenthelongwalls. TheshearresistanceforceRshallbethesumoftheshearresistanceforcesactingonthestabilizedbodyandthebottomoftheuntreatedsoil.
(6)Deformationofthesuperstructureduringactionofgroundmotiontendstobereducedbysoilimprovementbythedeepmixingmethod.Therefore,whensettingtheseismiccoefficientfortheverificationofthesuperstructureandtheimprovedsubsoilsystem,itispossibletosetarationalseismiccoefficientfortheverificationbasedonanappropriateevaluationofthisreductioneffect.
When soil improvement is performedby the deepmixingmethod the characteristic valuekh1k of the seismiccoefficientfortheverificationofthesuperstructureandthestructuralelementsofimprovedsubsoilsystemsuchassuperstructure,foundationmound,backfill,reclamationandsurchargecanbecalculatedbymultiplyingthemaximumvalueofcorrectedaccelerationαcobtainedfortheuntreatedgroundbythereductioncoefficient0.64,asshowninequation (4.5.9) 61).
(4.5.9)
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
where kh1k :characteristic value of seismic coefficient for verification of superstructure and structural
elements of improved subsoil system such as superstructure, foundation mound, backfill,reclamationandsurcharge
Da :allowabledeformation(cm) Dr :standarddeformation(=10cm) αc :maximumvalueofcorrectedacceleration(cm/s2) g :gravitationalacceleration(=980cm/s2)
This reductioncoefficientwasobtainedbasedon the resultsofa2-dimensionalnonlineareffective stressanalysis for untreated soil and improved subsoil. For details, Reference 61) can be used as a reference. Incalculatingthemaximumvalueofcorrectedaccelerationαcforuntreatedsoil,Chapter 5, 2.2.2 (1) S e i s m i c coefficient for verification used in verification of damage due to sliding and overturning of wall body and insufficient bearing capacity of foundation ground in variable situations in respect of Level 1 earthquake ground motion canbeusedasareference. Thecharacteristicvalueoftheseismiccoefficientforverificationofimprovedsubsoilkh2kcanbecalculatedbymultiplyingtheseismiccoefficientforverificationkh1kobtainedusingequation (4.5.9)bythereductioncoefficient0.65(kh2k=0.65xkh1k). Provided, however, that in the characteristic value of the seismic coefficient for verification kh3k used incalculations of the earth pressure during earthquakes for improved subsoil systems, in equation (4.5.9), themaximumvalueofcorrectedaccelerationshallnotbemultipliedbyareductioncoefficient.
L.W.L. R.W.L.
T
H
HW
C
P
C
P
tt
1
2
P
4
H6
55
W6
4
W
W8H8
H9 W9Pah
w
ua
pv
up * In case of wall-type improvement
dw
W1
H7
W7
H1
W2
H2
H3 W3
Untreated part
Stabilized part
<Vertical component><Vertical component>
Pph
Passive earth pressurePp
Pav
<Horizontal component><Horizontal component>
<Verticalcomponent><Verticalcomponent>
<Horizontalcomponent><Horizontalcomponent>
Waterpressure
Active earthpressure
Pa
Subgrade reaction
R* Block-type, wall-type (depend on slip pattern)
Fig. 4.5.6 External Forces Acting on Stabilized Body
Pa :resultantearthpressureperunitoflengthactingonverticalplaneofactiveside(kN/m) Pah :horizontalcomponentofresultantearthpressureperunitoflengthactingonverticalplaneof
activeside(kN/m) Pav :vertical componentof resultant earthpressureperunitof lengthactingonverticalplaneof
activeside(kN/m) Pp :resultantearthpressureperunitoflengthactingonverticalplaneofpassiveside(kN/m) Pph :horizontalcomponentofresultantearthpressureperunitoflengthactingonverticalplaneof
passiveside(kN/m) Ppv :vertical componentof resultant earthpressureperunitof lengthactingonverticalplaneof
passiveside(kN/m) Pw :resultantresidualwaterpressureperunitoflength(kN/m) Pdw :resultantdynamicwaterpressureperunitoflength(kN/m)
W1-W9 :weightperunitoflengthofeachpart(kN/m) H1-H9 :inertiaforceperunitoflengthofeachpart(kN/m)
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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Cua :resultantadhesionofverticalplaneperunitof lengthactingonverticalplaneofactiveside(kN/m)
Cup :resultantadhesionofverticalplaneperunitoflengthactingonverticalplaneofpassiveside(kN/m)
R :shearresistanceperunitoflengthactingonbottomofimprovedsubsoil(kN/m) T :resultantofsubgradereactionperunitoflengthactingonthebottomofimprovedsoil(kN/m) t1,t2 :intensityofsubgradereactionattoesofstabilizedbody(kN/m)
Intheperformanceverificationofactionsduringgroundmotionofstratawhicharesubjecttoliquefaction,itisnecessarytoconsiderthedynamicwaterpressureduringtheactionofgroundmotionontheimprovedbody.Forcalculationofdynamicwaterpressure,Part II, Chapter 5, 2 Water Pressurecanbeusedasareference.
4.5.4 Performance Verification
[1] External Stability of Improved Subsoil
Fortheexternalstabilityofimprovedsubsoil,thefollowingitemsshallbeexamined,assumingthatthestabilizedbodyandthesuperstructurebehaveintegrally.Itshouldbenotedthatthefollowingdescribesthecasesofgravity-typerevetmentsandquaywalls;however,thesamedescriptioncanalsobeappliedtobreakwatersbyappropriatelysettingactionsduetowavesandotherrelevantfactors.
(1)ExaminationofSliding61)
① Theimprovedsubsoilshallsecuretherequiredstabilityagainstslipfailure.
② Itisnecessarytoconductperformanceverificationofimprovedsubsoilbywall-typeimprovementfortwocases,namely, theslippattern1casewhichconsiders thefrictionalresistanceofthebottomoftheimprovedsubsoilasawholeasresistancetoslipfailure,andtheslippattern2casewhichconsiderstheresultantofthefrictionalresistancedirectlyunderthelongwallsandtheshearingresistanceoftheunimprovedsubsoilbetweenthewalls,consideringtheimprovedgroundtobeastructureinwhichthestabilizedsubsoillongwallsfullydemonstratesshearstrength.Intheexaminationofthestabilityagainstslipfailure,equation (4.5.10)canbeused.Thesymbolγintheequationisthepartialfactorforitssubscript,andthesubscriptskandddenotethecharacteristicvalueanddesignvalue,respectively.
(Slippattern1)
(Slippattern2)
(4.5.10)Provided,however,that
where R1 :frictionalresistanceofbearinggroundperunitoflengthactingonbottomofstabilizedbody
(kN/m) R2 :frictional resistanceofbearinggroundperunitof lengthactingonbottomofuntreatedsoil
(kN/m)
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
R3 :shearingresistanceperunitoflengthactingonbottomofuntreatedsoil(kN/m) Pw :resultantofresidualwaterpressureperunitoflength(kN/m) Pdw :resultantofdynamicwaterpressureduringearthquakeperunitoflength(kN/m) Hi :inertiaforceperunitoflengthactingonrespectiveparts(kN/m) Wi :weightperunitoflengthofsurcharge,superstructure,foundationmound,backfill,reclamation
onimprovedsubsoilcomprisingimprovedsubsoilsystem(kN/m) Ws :weightperunitoflengthofstabilizedbody(kN/m) W9 :weightperunitoflengthofuntreatedsoilbetweenlongwalls(kN/m) B :improvedwidthofstabilizedbody(m) Rl :ratiooflongwallinstabilizedbody Rs :ratioofshortwallinstabilizedbody μ :staticfrictioncoefficient Cu :shearstrengthofbottomofuntreatedsoil(kN/m2) Pah :horizontalcomponentofresultantearthpressureperunitoflengthactingonverticalplaneof
activeside(kN/m) Pav :vertical componentof resultant earthpressureperunitof lengthactingonverticalplaneof
activeside(kN/m) Pph :horizontalcomponentofresultantearthpressureperunitoflengthactingonverticalplaneof
passiveside(kN/m) Ppv :vertical componentof resultant earthpressureperunitof lengthactingonverticalplaneof
passiveside(kN/m) Cua :resultantadhesionofverticalplaneperunitof lengthactingonverticalplaneofactiveside
(kN/m) Cup :resultantadhesionofverticalplaneperunitoflengthactingonverticalplaneofpassiveside
(kN/m) ρwg :unitweightofseawater(kN/m3) RWL :residualwaterlevel(m) WL :waterlevelatfrontside(m) hL :waterdepthatbottomofstabilizedbody(m) h1 :waterdepthatfrontsideofstructure(m) kh1 :seismic coefficient for verification when calculating inertia force acting on surcharge,
superstructure, foundationmound,backfillandreclamationon improvedsubsoilcomprisingimprovedsubsoilsystem(kN/m)
kh2 :seismiccoefficientforverificationwhencalculatinginertiaforceactingonimprovedsubsoil kh3 :seismiccoefficientforverificationwhencalculatingearthpressureanddynamicwaterpressure
actingonimprovedsubsoilsystem Wni :weightperunitoflengthofsurcharge,superstructure,mainbody,foundationmound,backfill
andreclamationonimprovedsubsoilcomprisingimprovedsubsoilsystem.Ifsubmerged,theweightinairwhensaturatedwithwatershallbeused.(kN/m)
Wn8 :weightperunitoflengthofstabilizedbody.Ifsubmerged,theweightinairwhensaturatedwithwatershallbeused.(kN/m)
Wn9 :weightperunitoflengthofuntreatedsoilbetweenlongwalls.Ifsubmerged,theweightinairwhensaturatedwithwatershallbeused.(kN/m)
γi :structuralfactor,generallybeassumedtobe1.0 γa :structuralanalysisfactor,generallybeassumedtobe1.0
③ Thesystemreliability indexβT is setdependingon the individual facilitiesand improvedsubsoil. Incaseswheresoilimprovementiscarriedoutbythedeepmixingmethod,thesystemreliabilityindexβTforslidingandoverturningofthewallbody,failureduetoinsufficientbearingcapacityofthefoundationgroundofgravity-typequaywalls,failureduetotoepressure,verticalshearfailureofthelongwallpart,verticalshearfailureoftheshortwallpartandfailureduetoextrusionofuntreatedsubsoilbetweenthtelongwallswas2.9(failureprobabilityof2.1x10–3)forthePermanentsituation.Thiswastheresultofassessment,byreliabilitytheory,oftheaveragesafetylevelofgravity-typequaywallsforsoilimprovementbythedeepmixingmethodintheconventionaldesignmethod.Intheperformanceverificationdescribedhere,thetargetreliabilityindexofβT '=3.0foreachlimitstateissetsoastoexceedthesystemreliabilityindex.ThepartialfactorsdeterminedonthisbasisareasshowninTable 4.5.1throughTable 4.5.6.Forpartialfactorsforuseintheexaminationofslipfailureofimprovedsubsoil,thevaluesshowninTable 4.5.1maybeused.Forpartialfactorswhicharenotlistedinthetable,1.00maybeused.
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
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Table 4.5.1 Standard Values of Partial Factors for Use in Examination of Slip Failure(a) Permanent situation
AllfacilitiesTargetreliabilityindexβT 2.9
TargetsystemfailureprobabilityPfT 2.1×10–3
Reliabilityindexβusedincalculationofγ 3.0γ α µ/Xk V
Slippattern1 γW1-γW9 Weight 1.00 0.131 1.00 0.03γPah Horizontalresultantofactiveearthpressure 1.15 –0.519 1.00 0.10γPav Verticalresultantofactiveearthpressure 1.00 0.000 1.00 –γPph Horizontalresultantofpassiveearth
pressure0.90 0.277 1.00 0.10
γPpv Verticalresultantofpassiveearthpressure 1.00 0.000 1.00 –γCua Adhesionofverticalplane(activeside) 1.00 0.000 1.00 –γCup Adhesionofverticalplane(passiveside) 1.00 0.000 1.00 –γµ Staticfrictioncoefficient 0.70 1.000 1.00 0.10γa Structuralanalysisfactor 1.00 – – –
Slippattern2 γW1-γW9 Weight 1.00 0.000 1.00 –γPah Horizontalresultantofactiveearthpressure 1.15 –0.461 1.00 0.10γPav Verticalresultantofactiveearthpressure 1.00 0.000 1.00 –γPph Horizontalresultantofpassiveearth
pressure0.85 0.454 1.00 0.10
γPpv Verticalresultantofpassiveearthpressure 1.00 0.000 1.00 –γCua Adhesionofverticalplane(activeside) 1.00 0.000 1.00 –γCup Adhesionofverticalplane(passiveside) 1.00 0.000 1.00 –γµ Staticfrictioncoefficient 0.75 0.831 1.00 0.10γcu Shearstrengthofbottomofunimproved
subsoil0.80 0.202 1.00 0.33
γa Structuralanalysisfactor 1.00 – – –
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
(b) Variable situations in respect of Level 1 earthquake ground motion
AllfacilitiesPerformancerequirement Serviceability
γ α µ/Xk VSlippattern1 γW1-γW9 Weight 1.00 – – –
γPah Horizontalresultantofactiveearthpressure 1.00 – – –γPav Verticalresultantofactiveearthpressure 1.00 – – –γPph Horizontalresultantofpassiveearth
pressure1.00 – – –
γPpv Verticalresultantofpassiveearthpressure 1.00 – – –γCua Adhesionofverticalplane(activeside) 1.00 – – –γCup Adhesionofverticalplane(passiveside) 1.00 – – –γµ Staticfrictioncoefficient 1.00 – – –γa Structuralanalysisfactor 1.00 – – –
Slippattern2 γW1-γW9 Weight 1.00 – – –γPah Horizontalresultantofactiveearthpressure 1.00 – – –γPav Verticalresultantofactiveearthpressure 1.00 – – –γPph Horizontalresultantofpassiveearth
pressure1.00 – – –
γPpv Verticalresultantofpassiveearthpressure 1.00 – – –γCua Adhesionofverticalplane(activeside) 1.00 – – –γCup Adhesionofverticalplane(passiveside) 1.00 – – –γµ Staticfrictioncoefficient 1.00 – – –γcu Shearstrengthofbottomofunimproved
subsoil1.00 – – –
γa Structuralanalysisfactor 1.00 – – –
(2)ExaminationofOverturning61)
① Itisnecessarythatimprovedsubsoilsecuretherequiredstabilityagainstoverturning.Intheexaminationofthestabilityagainstoverturningofimprovedsubsoilbywall-typeimprovement,equation (4.5.11)andequation (4.5.12)canbeused.Intheseequations,thesymbolγisthepartialfactorforitssubscript,andthesubscriptskandddenotethecharacteristicvalueanddesignvalue,respectively.
(a) Permanentsituation
(4.5.11)
(b)VariablesituationsinrespectofLevel1earthquakegroundmotion
(4.5.12)Provided,however,that
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
–509–
whereItemsrelatedtoresistance
Pph :horizontalcomponentofresultantofearthpressureperunitoflengthactingonverticalplaneofpassiveside(kN/m)
Wi :weight per unit of length of surcharge, superstructure, foundation rubble, backfill andreclamationonimprovedsubsoilcomprisingimprovedsubsoilsystem(kN/m)
W8 :weightperunitoflengthofstabilizedbody(kN/m) W9 :weightperunitoflengthofuntreatedsoilbetweenlongwalls(kN/m) Pav :verticalcomponentofresultantofearthpressureperunitoflengthactingonverticalplaneof
activeside(kN/m) Cua :adhesionofverticalsideperunitoflengthactingonverticalplaneofactiveside(kN/m)
Itemsrelatedtoloads Pw :residualwaterpressureperunitoflengthactingonverticalplaneofactiveside(kN/m) Pah :horizontalcomponentofresultantofearthpressureperunitoflengthactingonverticalplaneof
activeside(kN/m) Hi :inertiaforceperunitoflengthactingonrespectivepartsofimprovedsubsoilsystem(kN/m) Wni :weight per unit of length of surcharge, superstructure, foundation mound, backfill and
reclamation on improved subsoil comprising improved subsoil system. If submerged, theweightinairwhensaturatedwithwatershallbeused.(kN/m)
Wn8 :weightperunitoflengthofstabilizedbody.Ifsubmerged,theweightinairwhensaturatedwithwatershallbeused.(kN/m)
Wn9 :weightperunitoflengthofuntreatedsoilbetweenlongwalls.Ifsubmerged,theweightinairwhensaturatedwithwatershallbeused.(kN/m)
kh1 :seismic coefficient for verification when calculating inertia force acting on surcharge,superstructure,foundationmound,backfill,back–pluggingandsurchargeonimprovedsubsoilcomprisingimprovedsubsoilsystem
kh2 :seismiccoefficientforverificationwhencalculatinginertiaforceactingonimprovedsubsoil kh3 :seismiccoefficientforverificationwhencalculatingearthpressureandactivewaterpressure
actingonimprovedsubsoil Pdw :dynamicwaterpressureperunitoflengthactingonverticalplaneofactiveside(kN/m)
xi,xav,xcua:distancefromactionlineofverticalforceactingonimprovedsubsoiltofronttoeofstabilized body(m)
γi,γp, γw, γdw :heightfromactionlineofhorizontalforceactingonimprovedsubsoiltobottomofstabilized body(m) γi :structuralfactor,generallybeassumedtobe1.0 γa :structuralanalysisfactor(see Table 4.5.2)
② Forpartialfactorsforuseintheexaminationofoverturningofimprovedsubsoil,thevaluesshowninTable 4.5.2maybeused.Forpartialfactorsnotlistedinthetable,1.00maybeused.
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
Table 4.5.2 Standard Values of Partial Factors for Use in Examination of Overturning (a) Permanent situation
AllfacilitiesTargetreliabilityindexβT 2.9
TargetsystemfailureprobabilityPfT 2.1×10–3
Reliabilityindexβusedincalculationofγ 3.0γ α µ/Xk V
Overturning γPph Horizontalresultantofpassiveearthpressure
0.85 0.382 1.00 0.10
γW6 Weight(foundationmound) 1.00 0.030 1.00 0.03γW7 Weight(backfillsoil) 1.00 0.055 1.00 0.03γW8 Weight(stabilizedbody) 1.00 0.102 1.00 0.03γW9 Weight(untreatedsoil) 1.00 0.074 1.00 0.03γCua Adhesionofverticalplane(stabilizedbody
part:activeside)1.00 0.102 1.00 0.10
γPah Horizontalresultantofactiveearthpressure 1.25 –0.882 1.00 0.10γPav Verticalresultantofactiveearthpressure 1.00 0.029 1.00 0.10γa Structuralanalysisfactor 1.00 – – –
(b) Variable situations in respect of Level 1 earthquake ground motion
AllfacilitiesPerformancerequirement Serviceability
γ α µ/Xk VOverturning γPph Horizontalresultantofpassiveearth
pressure1.00 – – –
γW6 Weight(foundationmound) 1.00 – – –γW7 Weight(backfillsoil) 1.00 – – –γW8 Weight(stabilizedbody) 1.00 – – –γW9 Weight(untreatedsoil) 1.00 – – –γCua Adhesionofverticalplane(stabilizedbody
part:activeside)1.00 – – –
γPah Horizontalresultantofactiveearthpressure 1.00 – – –γPav Verticalresultantofactiveearthpressure 1.00 – – –γa Structuralanalysisfactor 1.10 – – –
(3)ExaminationofBearingCapacity61)
① Improvedsubsoilshallsecuretherequiredstabilityagainstfailureofbearingcapacityoftheoriginalgroundunderthebottomoftheimprovedsubsoil.Intheexaminationofthebearingcapacityofblock-typeimprovedsubsoil,2.2 Shallow Spread Foundationscanbeusedasareference.
② For thebearing capacityof improved subsoil bywall-type improvementwhen thebearingground is sandyground,verificationcanbeperformedusingequation(4.5.13) fortoepressurest1andt2,consideringtheeffectofmutualinterferencebetweenthelongwalls.Inthisequation,thesymbolγisthepartialfactorforitssubscript,andthesubscriptskandddenotethecharacteristicvalueanddesignvalue,respectively.
Inthecaseof (4.5.13)inthecaseof
where
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
–511–
γR :partialfactorforbearingcapacityofsandyground(see2.2.2 Bearing Capacity of Foundations on Sandy Ground)
Nq,Nr:bearingcapacitycoefficients(see2.2.2 Bearing Capacity of Foundations on Sandy Ground) p0 :effectiveoverburdenpressuretobearingsandlayer(kN/m2) ρg :unitweightofbearingground,whensubmerged,unitweightinwater(kN/m3)
Ll :lengthoflongwallindirectionoffaceline(m)(seeFig. 4.5.9) Ls :lengthofshortwallindirectionoffaceline(m)(seeFig. 4.5.9) B :improvementwidth(m)(seeFig. 4.5.9)
[2] Examination of Internal Stability
(1)Forthecharacteristicvalueofthematerialstrengthofthestabilizedbody,4.5.2 Assumption of Dimensions of Stabilized Body canbeusedasareference.
(2)Thestressgeneratedinthestabilizedbodycanbeobtainedbyassumingthatthestabilizedbodyisanelasticbodyundertheconditionsspecifiedin4.5.3 Conditions of Actions on Stabilized Body.
(3)In block-type improved subsoil and improved subsoil by wall-type improvement, internal stability can beexaminedbythemethodpresentedbelow.Provided,however,thatincaseswheretheshapeofthestabilizedbodyiscomplexorthedepthofthestabilizedbodyislargeincomparisonwithitswidth,examinationbyFEManalysisispreferable.
(4)ExaminationofToePressure61)
① Examinationof internal stabilitydue to toepressureat thebottomof thestabilizedbodycanbeperformedusingequation(4.5.14),consideringtheeffectoftheconfiningpressureactingontheimprovedsubsoil.Inthisequation,thesymbolγisthepartialfactorforitssubscript,andthesubscriptskandddenotethecharacteristicvalueanddesignvalue,respectively.
(4.5.14)
where fc :designcompressivestrength(kN/m2) t1, 2 :toepressures(kN/m2) K :coefficientofearthpressure wi :unitweightofuntreatedsoil,whensubmerged,unitweightinwater(kN/m3) hi :layerthicknessofuntreatedsubsoil(m) γi :structuralfactor,generallybeassumedtobe1.0 γa :structuralanalysisfactor,generallybeassumedtobe1.0
Thedesignvaluesintheequationcanbeobtainedusingthefollowingequations.
Provided,however,thatitisnecessarytodeterminethevalueoftheconfiningpressureKΣ(widhi)actingonthebottomedgeofthestabilizedbodyfromtheuntreatedsubsoilconsideringtheimprovementpatternandexternalstabilityoftheimprovedsubsoil.
② Forthepartialfactorsforuseinexaminationoftoepressure,thevaluesshowninTable 4.5.3maybeused.Forpartialfactorsnotlistedinthetable,1.00maybeused.
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
Table 4.5.3 Standard Values of Partial Factors for Use in Examination of Toe Pressure
(a) Permanent situation
AllfacilitiesTargetreliabilityindexβT 2.9
TargetsystemfailureprobabilityPfT 2.1×10–3
Reliabilityindexβusedincalculationofγ 3.0γ α µ/Xk V
Toepressure γquc Standarddesignstrength 0.55 – – –γt1,2 Toepressure 1.05 –0.116 1.00 0.03γwi Unitweightofuntreatedsoil 1.00 0.001 1.00 0.03γa Structuralanalysisfactor 1.00 – – –
(b) Variable situations in respect of Level 1 earthquake ground motion
AllfacilitiesPerformancerequirement Serviceability
γ α µ/Xk VToepressure γquc Standarddesignstrength 0.67 – – –
γt1,2 Toepressure 1.00 – – –
γwi Unitweightofuntreatedsoil 1.00 – – –γa Structuralanalysisfactor 1.00 – – –
(5)ExaminationofShearingStressatVerticalPlaneUnderFaceLineofSuperstructure61)
① Examinationofinternalstabilityagainstshearingstressalongtheverticalplanebeneaththefacelineofthesuperstructurecanbeperformedforthelongwallpartandshortwallpartusingequation (4.5.15)andequation (4.5.16),respectively.Intheseequations,thesymbolγisthepartialfactorforitssubscript,andthesubscriptskandddenotethecharacteristicvalueanddesignvalue,respectively.
(a) Longwall
(4.5.15)where
α :factorforeffectivecross-sectionalarea β :reliabilityindexofoverlapbetweenimprovedpiles Tl :resultantofsubgradereactionactingfromfronttoeofimprovedsubsoiltopositionofBl(kN)
(Tld=γTTl) quc :standarddesignstrength(kN/m2)(qucd = γqucquck) Wl :effectiveweightofstabilizedbodyfromfronttoeofimprovedsubsoiltopositionofBl(kN)(Wld
=γwWl) A :cross-sectionalareaofstabilizedbody,incaseoflongwallA=DlLl +DsLs(m2)(seeFig. 7.5.7)
Dl,Ds :verticallengthoflongwall,namelyimproveddepth,andverticallengthofshortwall(m)Ll,Ls :lengthsoflongwallandshortwallindirectionoffaceline,respectively(m) γi :structuralfactor,generallybeassumedtobe1.0 γa :structuralanalysisfactor,generallybeassumedtobe1.0
Whena rubblemoundexistsbetween the stabilizedbodyand the superstructure, examinationmaybeperformedusinganexaminationplanewhichconsidersloaddispersioninthemoundfromthepositionofthefacelineofthesuperstructure.(SeeFig. 4.5.7;θistheangleofloaddispersioninthemound.)
PART III FACILITIES, CHAPTER 2 ITEMS COMMON TO FACILITIES SUBJECT TO TECHNICAL STANDARDS
–513–
B
D
DD
θsA
LsT
B
W
L
Fig. 4.5.7 Schematic Diagram of Vertical Shear Stress (Long Wall)
Forthepartialfactorsforuseintheexaminationofverticalshearfailureofthelongwallpart,thevaluesshowninTable 4.5.4canbeused.Forpartialfactorswhicharenotlistedinthetable,1.00maybeused.
Table 4.5.4 Standard Values of Partial Factors for Use in Examination of Vertical Shear Failure of Long Wall
(a) Permanent situation
AllfacilitiesTargetreliabilityindexβT 2.9
TargetsystemfailureprobabilityPfT 2.1×10–3
Reliabilityindexβusedincalculationofγ 3.0γ α µ/Xk V
Verticalshearfailureoflongwall
γquc Standarddesignstrength 0.55 – – –γT Resultantofsubgradereaction 1.05 –0.115 1.00 0.03γW Effectiveweightofstabilizedbody 1.00 0.005 1.00 0.03γa Structuralanalysisfactor 1.00 – – –
(b) Variable situations in respect of Level 1 earthquake ground motion
AllfacilitiesPerformancerequirement Serviceability
γ α µ/Xk VVerticalshearfailureoflongwall
γquc Standarddesignstrength 0.67 – – –γT Resultantofsubgradereaction 1.00 – – –γWℓ Effectiveweightofstabilizedbody 1.00 – – –γa Structuralanalysisfactor 1.00 – – –
(b)Shortwall
(4.5.16)where
α : factorforeffectivecross-sectionalareaβ : reliabilityindexofoverlapbetweenimprovedpilesTl’: toepressureafterdispersioninmound,notincludingself–weightofmound(kN/m2)(Tl’d=γT lT’l’k) (seeFig. 4.5.8)(kN)
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
quc :standarddesignstrength(kN/m2)(qucd = γqucquck) wm :unitweightofmound,whensubmerged,unitweightinwater(kN/m3) hm :thicknessofmound(m) Wl :effectiveweightofstabilizedbody,whensubmerged,unitweightinwater(kN/m3) Ds :verticallengthofshortwall(m) Ls :lengthofshortwallindirectionoffaceline(m) γi :structuralfactor,generallybeassumedtobe1.0 γa :structuralanalysisfactor,generallybeassumedtobe1.0
Fig. 4.5.8 Schematic Diagram of Calculation of Vertical Shear Stress (Short Wall)
Forthepartialfactorsforuseinexaminationofverticalshearfailureoftheshortwall,thevaluesshowninTable 4.5.5canbeused.Forpartialfactorswhicharenotlistedinthetable,1.00maybeused.
Table 4.5.5 Standard Values of Partial Factors for Use in Examination of Vertical Shear Failure of Short Wall
(a) Permanent situation
AllfacilitiesTargetreliabilityindexβT 2.9
TargetsystemfailureprobabilityPfT 2.1×10–3
Reliabilityindexβusedincalculationofγ 3.0γ α µ/Xk V
Verticalshearfailureofshortwall
γquc Standarddesignstrength 0.55 – – –γT1' Toepressure 1.05 –0.091 1.00 0.03γwi Unitweightofstabilizedbody 1.00 –0.006 1.00 0.03γwm Unitweightofmound 1.00 –0.006 1.00 0.03γa Structuralanalysisfactor 1.00 – – –
(b) Variable situations in respect of Level 1 earthquake ground motion
AllfacilitiesPerformancerequirement Serviceability
γ α µ/Xk VVerticalshearfailureofshortwall
γquc Standarddesignstrength 0.67 – – –γT1' Toepressure 1.00 – – –γwi Unitweightofstabilizedbody 1.00 – – –γwm Unitweightofmound 1.00 – – –γa Structuralanalysisfactor 1.00 – – –
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(6)ExaminationofExtrusion61)
① Becauseimprovedsubsoilbywall-typeimprovementcomprisesalargenumberoflongwallsandashortwallconnecting the longwalls,untreatedsubsoil is leftbetween the longwalls. Failures inwhich theuntreatedsubsoil between the longwalls is dislodged are conceivable, depending on conditions such as the spacingbetweenthelongwalls,thestrengthoftheuntreatedsubsoil,thethicknessofthebackfilllayer.Therefore,itisnecessarytoexamineextrusionoftheuntreatedsoilbetweenthelongwalls.71)
② Aschematicdiagramofextrusionoftheuntreatedsoilinimprovedsubsoilbywall-typeimprovementisshowninFig. 4.5.9.
Fig. 4.5.9 Schematic Diagram of Extrusion of Untreated Subsoil
③ Examinationofextrusionofuntreatedsubsoilbetweenlongwallscanbeperformedbyrepeatedcalculationsusingequation(4.5.17),usingvariousvaluesofDiinthecalculations.
(4.5.17)where
Ls :lengthofshortwallindirectionoffaceline(m) Di :depthfrombottomedgeofshortwalltocross–sectionbeingexamined(m) Cu :averageshearstrengthofuntreatedsubsoilatintermediatedepthbetweenbottomedgeofshort
wallandcrosssectionbeingexamined(kN/m2)(C=γcuCuk) B :improvedwidth(m)
Pah’,Pph’:horizontalcomponentsofresultantofactiveearthpressureandpassiveearthpressureactingonuntreatedsubsoilbetweenlongwalls,respectively,downtothedepthofDifrombottomofshortwall(kN)(Pph’d=γPphPph’d,Pah’d =γPahPah’k)
kh2 :seismiccoefficientforverificationwhencalculatinginertiaforceactingonimprovedsubsoil(kh2d=γkh2kh2k)
hw :headbetweenresidualwaterlevelandwaterlevelatfrontofstructure(m)(hwd=γhwhwk) wi :unitweightinairofuntreatedsubsoilwhensaturatedwithwater(kN/m3)ρwg :unitweightofseawater(kN/m3) γi :structuralfactor,generallyassumedtobe1.0 γa :structuralanalysisfactor,generallyassumedtobe1.0
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TECHNICAL STANDARDS AND COMMENTARIES FOR PORT AND HARBOUR FACILITIES IN JAPAN
④ Forthepartialfactorsforuseintheexaminationoftheextrusionoftheuntreatedsubsoilbetweenlongwalls,thevaluesshowninTable 4.5.6canbeused.Forpartialfactorswhicharenotlistedinthetable,1.00maybeused.
Table 4.5.6 Standard Values of Partial Factors for Use in Examination of Extrusion(a) Permanent situation
AllfacilitiesTargetreliabilityindexβT 2.9
TargetsystemfailureprobabilityPfT 2.1×10–3
Reliabilityindexβusedincalculationofγ 3.0γ α µ/Xk V
Extrusionfailure
γCu Averageshearstrengthofuntreatedsoil 0.75 0.955 1.00 0.10γPah' Horizontalcomponentofresultantofactive
earthpressureactingonuntreatedsoilbetweenlongwalls
1.05 –0.190 1.00 0.10
γPph' Horizontalcomponentofresultantofpassiveearthpressureactingonuntreatedsoilbetweenlongwalls
0.95 0.182 1.00 0.10
γwi Unitweightinairofuntreatedsoilwhensaturatedwithwater
1.00 0.000 1.00 0.10
γa Structuralanalysisfactor 1.00 – – –
* Thepartialfactorsforuseinexaminationofextrusionweredeterminedbyreliabilityanalysisoftheexaminationposition(Di)atwhichthereliabilityindexβshowsitsminimumvalue.
(b) Variable situations in respect of Level 1 earthquake ground motion
AllfacilitiesPerformancerequirement Serviceability
γ α µ/Xk VExtrusionfailure
γCu Averageshearstrengthofuntreatedsoil 1.00 – – –γPah' Horizontalcomponentofresultantofactive
earthpressureactingonuntreatedsoilbetweenlongwalls
1.00 – – –
γPph' Horizontalcomponentofresultantofpassiveearthpressureactingonuntreatedsoilbetweenlongwalls
1.00 – – –
γwi Unitweightinairofuntreatedsoilwhensaturatedwithwater
1.00 – – –
γa Structuralanalysisfactor 1.00 – – –
* Thepartialfactorsforuseinexaminationofextrusionweredeterminedbyreliabilityanalysisoftheexaminationposition(Di)atwhichthereliabilityindexβshowsitsminimumvalue.
(7)ExaminationofCircularSlipFailure
① Intheexaminationofthecircularslipfailure,3 Stability of Slopescanbeusedasareference.
② Becausethestrengthofthestabilizedbodyissufficientlygreaterthanthatofordinarysoil,examinationofslipcirclespassingthroughthestabilizedbodymaybeomitted.
(8)ExaminationofDisplacement
①Whentheimprovedsubsoilisofthefloatingtype,lateraldisplacementduetoactionsinrespectofreclamationand waves and actions in respect of ground motion, and vertical displacement due to consolidation areconceivable.Therefore,advanceexaminationonmeasurescapableofsatisfyingtheperformancerequirementsofthefacilitiesisnecessary,basedonestimationsofthesedisplacements.
② Inslidingfailureandcircularslipfailureofimprovedsubsoil,thereisacertaindegreeofrelationshipbetweentheratioofthedesignvalueofresistanceanddesignvalueoftheeffectsofactions,andtheamountofimmediatedisplacementduetolateraldisplacementofthestabilizedbody.Therefore,itispossibletojudgethenecessityofexaminationoflateraldisplacementofthestabilizedbodydependingonthesafetymargininthesefactors.Furthermore,whenthelayerthicknessoftheuntreatedsubsoilunderneaththestabilizedbodyisconstant,and
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itisjudgedthattheestimateddisplacementinthehorizontaldirectioncansatisfytheperformancerequirementsofthefacilities,theexaminationoftheconsolidationsettlementisonlynecessary.
③ Even inbottom seated-type improved subsoil,when a cohesive soil layer exists under thebearing stratum,the examination of the amount of consolidation settlement is necessary, as there is a possibility of verticaldisplacementofthestabilizedbodyduetoconsolidationsettlement.
④ It is preferable to determine the allowable displacement of improved subsoil appropriately, considering theperformancerequirementsofthefacilities.